[I'm going to send a pull request tomorrow if nobody yells;
please review and test - it seems to work fine here, but extra
eyes and extra testing would be very welcome]
passing kmap_local_page() result to __kernel_write() is unsafe -
random ->write_iter() might (and 9p one does) get unhappy when
passed ITER_KVEC with pointer that came from kmap_local_page().
Fix by providing a variant of __kernel_write() that takes an iov_iter
from caller (__kernel_write() becomes a trivial wrapper) and adding
dump_emit_page() that parallels dump_emit(), except that instead of
__kernel_write() it uses __kernel_write_iter() with ITER_BVEC source.
Fixes: 3159ed57792b "fs/coredump: use kmap_local_page()"
Signed-off-by: Al Viro <[email protected]>
---
diff --git a/fs/coredump.c b/fs/coredump.c
index 9f4aae202109..09dbc981ad5c 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -832,6 +832,38 @@ static int __dump_skip(struct coredump_params *cprm, size_t nr)
}
}
+static int dump_emit_page(struct coredump_params *cprm, struct page *page)
+{
+ struct bio_vec bvec = {
+ .bv_page = page,
+ .bv_offset = 0,
+ .bv_len = PAGE_SIZE,
+ };
+ struct iov_iter iter;
+ struct file *file = cprm->file;
+ loff_t pos = file->f_pos;
+ ssize_t n;
+
+ if (cprm->to_skip) {
+ if (!__dump_skip(cprm, cprm->to_skip))
+ return 0;
+ cprm->to_skip = 0;
+ }
+ if (cprm->written + PAGE_SIZE > cprm->limit)
+ return 0;
+ if (dump_interrupted())
+ return 0;
+ iov_iter_bvec(&iter, WRITE, &bvec, 1, PAGE_SIZE);
+ n = __kernel_write_iter(cprm->file, &iter, &pos);
+ if (n != PAGE_SIZE)
+ return 0;
+ file->f_pos = pos;
+ cprm->written += PAGE_SIZE;
+ cprm->pos += PAGE_SIZE;
+
+ return 1;
+}
+
int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
{
if (cprm->to_skip) {
@@ -863,7 +895,6 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
for (addr = start; addr < start + len; addr += PAGE_SIZE) {
struct page *page;
- int stop;
/*
* To avoid having to allocate page tables for virtual address
@@ -874,12 +905,7 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
*/
page = get_dump_page(addr);
if (page) {
- void *kaddr = kmap_local_page(page);
-
- stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
- kunmap_local(kaddr);
- put_page(page);
- if (stop)
+ if (!dump_emit_page(cprm, page))
return 0;
} else {
dump_skip(cprm, PAGE_SIZE);
diff --git a/fs/internal.h b/fs/internal.h
index 87e96b9024ce..3e206d3e317c 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -16,6 +16,7 @@ struct shrink_control;
struct fs_context;
struct user_namespace;
struct pipe_inode_info;
+struct iov_iter;
/*
* block/bdev.c
@@ -221,3 +222,5 @@ ssize_t do_getxattr(struct user_namespace *mnt_userns,
int setxattr_copy(const char __user *name, struct xattr_ctx *ctx);
int do_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
struct xattr_ctx *ctx);
+
+ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos);
diff --git a/fs/read_write.c b/fs/read_write.c
index 1a261dcf1778..328ce8cf9a85 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -496,14 +496,9 @@ static ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t
}
/* caller is responsible for file_start_write/file_end_write */
-ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos)
+ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos)
{
- struct kvec iov = {
- .iov_base = (void *)buf,
- .iov_len = min_t(size_t, count, MAX_RW_COUNT),
- };
struct kiocb kiocb;
- struct iov_iter iter;
ssize_t ret;
if (WARN_ON_ONCE(!(file->f_mode & FMODE_WRITE)))
@@ -519,8 +514,7 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
init_sync_kiocb(&kiocb, file);
kiocb.ki_pos = pos ? *pos : 0;
- iov_iter_kvec(&iter, WRITE, &iov, 1, iov.iov_len);
- ret = file->f_op->write_iter(&kiocb, &iter);
+ ret = file->f_op->write_iter(&kiocb, from);
if (ret > 0) {
if (pos)
*pos = kiocb.ki_pos;
@@ -530,6 +524,18 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
inc_syscw(current);
return ret;
}
+
+/* caller is responsible for file_start_write/file_end_write */
+ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos)
+{
+ struct kvec iov = {
+ .iov_base = (void *)buf,
+ .iov_len = min_t(size_t, count, MAX_RW_COUNT),
+ };
+ struct iov_iter iter;
+ iov_iter_kvec(&iter, WRITE, &iov, 1, iov.iov_len);
+ return __kernel_write_iter(file, &iter, pos);
+}
/*
* This "EXPORT_SYMBOL_GPL()" is more of a "EXPORT_SYMBOL_DONTUSE()",
* but autofs is one of the few internal kernel users that actually
Al Viro <[email protected]> writes:
> [I'm going to send a pull request tomorrow if nobody yells;
> please review and test - it seems to work fine here, but extra
> eyes and extra testing would be very welcome]
>
> passing kmap_local_page() result to __kernel_write() is unsafe -
> random ->write_iter() might (and 9p one does) get unhappy when
> passed ITER_KVEC with pointer that came from kmap_local_page().
>
> Fix by providing a variant of __kernel_write() that takes an iov_iter
> from caller (__kernel_write() becomes a trivial wrapper) and adding
> dump_emit_page() that parallels dump_emit(), except that instead of
> __kernel_write() it uses __kernel_write_iter() with ITER_BVEC source.
Acked-by: "Eric W. Biederman" <[email protected]>
From a 10,000 foot view this makes sense.
> Fixes: 3159ed57792b "fs/coredump: use kmap_local_page()"
> Signed-off-by: Al Viro <[email protected]>
> ---
> diff --git a/fs/coredump.c b/fs/coredump.c
> index 9f4aae202109..09dbc981ad5c 100644
> --- a/fs/coredump.c
> +++ b/fs/coredump.c
> @@ -832,6 +832,38 @@ static int __dump_skip(struct coredump_params *cprm, size_t nr)
> }
> }
>
> +static int dump_emit_page(struct coredump_params *cprm, struct page *page)
> +{
> + struct bio_vec bvec = {
> + .bv_page = page,
> + .bv_offset = 0,
> + .bv_len = PAGE_SIZE,
> + };
> + struct iov_iter iter;
> + struct file *file = cprm->file;
> + loff_t pos = file->f_pos;
> + ssize_t n;
> +
> + if (cprm->to_skip) {
> + if (!__dump_skip(cprm, cprm->to_skip))
> + return 0;
> + cprm->to_skip = 0;
> + }
> + if (cprm->written + PAGE_SIZE > cprm->limit)
> + return 0;
> + if (dump_interrupted())
> + return 0;
> + iov_iter_bvec(&iter, WRITE, &bvec, 1, PAGE_SIZE);
> + n = __kernel_write_iter(cprm->file, &iter, &pos);
> + if (n != PAGE_SIZE)
> + return 0;
> + file->f_pos = pos;
> + cprm->written += PAGE_SIZE;
> + cprm->pos += PAGE_SIZE;
> +
> + return 1;
> +}
> +
> int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
> {
> if (cprm->to_skip) {
> @@ -863,7 +895,6 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
>
> for (addr = start; addr < start + len; addr += PAGE_SIZE) {
> struct page *page;
> - int stop;
>
> /*
> * To avoid having to allocate page tables for virtual address
> @@ -874,12 +905,7 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
> */
> page = get_dump_page(addr);
> if (page) {
> - void *kaddr = kmap_local_page(page);
> -
> - stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
> - kunmap_local(kaddr);
> - put_page(page);
> - if (stop)
> + if (!dump_emit_page(cprm, page))
> return 0;
> } else {
> dump_skip(cprm, PAGE_SIZE);
> diff --git a/fs/internal.h b/fs/internal.h
> index 87e96b9024ce..3e206d3e317c 100644
> --- a/fs/internal.h
> +++ b/fs/internal.h
> @@ -16,6 +16,7 @@ struct shrink_control;
> struct fs_context;
> struct user_namespace;
> struct pipe_inode_info;
> +struct iov_iter;
>
> /*
> * block/bdev.c
> @@ -221,3 +222,5 @@ ssize_t do_getxattr(struct user_namespace *mnt_userns,
> int setxattr_copy(const char __user *name, struct xattr_ctx *ctx);
> int do_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
> struct xattr_ctx *ctx);
> +
> +ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos);
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 1a261dcf1778..328ce8cf9a85 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -496,14 +496,9 @@ static ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t
> }
>
> /* caller is responsible for file_start_write/file_end_write */
> -ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos)
> +ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos)
> {
> - struct kvec iov = {
> - .iov_base = (void *)buf,
> - .iov_len = min_t(size_t, count, MAX_RW_COUNT),
> - };
> struct kiocb kiocb;
> - struct iov_iter iter;
> ssize_t ret;
>
> if (WARN_ON_ONCE(!(file->f_mode & FMODE_WRITE)))
> @@ -519,8 +514,7 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
>
> init_sync_kiocb(&kiocb, file);
> kiocb.ki_pos = pos ? *pos : 0;
> - iov_iter_kvec(&iter, WRITE, &iov, 1, iov.iov_len);
> - ret = file->f_op->write_iter(&kiocb, &iter);
> + ret = file->f_op->write_iter(&kiocb, from);
> if (ret > 0) {
> if (pos)
> *pos = kiocb.ki_pos;
> @@ -530,6 +524,18 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
> inc_syscw(current);
> return ret;
> }
> +
> +/* caller is responsible for file_start_write/file_end_write */
> +ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos)
> +{
> + struct kvec iov = {
> + .iov_base = (void *)buf,
> + .iov_len = min_t(size_t, count, MAX_RW_COUNT),
> + };
> + struct iov_iter iter;
> + iov_iter_kvec(&iter, WRITE, &iov, 1, iov.iov_len);
> + return __kernel_write_iter(file, &iter, pos);
> +}
> /*
> * This "EXPORT_SYMBOL_GPL()" is more of a "EXPORT_SYMBOL_DONTUSE()",
> * but autofs is one of the few internal kernel users that actually
On Tue, Sep 27, 2022 at 11:51:17PM +0100, Al Viro wrote:
> [I'm going to send a pull request tomorrow if nobody yells;
> please review and test - it seems to work fine here, but extra
> eyes and extra testing would be very welcome]
... and now with page leak fixed:
commit 06bbaa6dc53cb72040db952053432541acb9adc7
Author: Al Viro <[email protected]>
Date: Mon Sep 26 11:59:14 2022 -0400
[coredump] don't use __kernel_write() on kmap_local_page()
passing kmap_local_page() result to __kernel_write() is unsafe -
random ->write_iter() might (and 9p one does) get unhappy when
passed ITER_KVEC with pointer that came from kmap_local_page().
Fix by providing a variant of __kernel_write() that takes an iov_iter
from caller (__kernel_write() becomes a trivial wrapper) and adding
dump_emit_page() that parallels dump_emit(), except that instead of
__kernel_write() it uses __kernel_write_iter() with ITER_BVEC source.
Fixes: 3159ed57792b "fs/coredump: use kmap_local_page()"
Signed-off-by: Al Viro <[email protected]>
diff --git a/fs/coredump.c b/fs/coredump.c
index 9f4aae202109..1ab4f5b76a1e 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -832,6 +832,38 @@ static int __dump_skip(struct coredump_params *cprm, size_t nr)
}
}
+static int dump_emit_page(struct coredump_params *cprm, struct page *page)
+{
+ struct bio_vec bvec = {
+ .bv_page = page,
+ .bv_offset = 0,
+ .bv_len = PAGE_SIZE,
+ };
+ struct iov_iter iter;
+ struct file *file = cprm->file;
+ loff_t pos = file->f_pos;
+ ssize_t n;
+
+ if (cprm->to_skip) {
+ if (!__dump_skip(cprm, cprm->to_skip))
+ return 0;
+ cprm->to_skip = 0;
+ }
+ if (cprm->written + PAGE_SIZE > cprm->limit)
+ return 0;
+ if (dump_interrupted())
+ return 0;
+ iov_iter_bvec(&iter, WRITE, &bvec, 1, PAGE_SIZE);
+ n = __kernel_write_iter(cprm->file, &iter, &pos);
+ if (n != PAGE_SIZE)
+ return 0;
+ file->f_pos = pos;
+ cprm->written += PAGE_SIZE;
+ cprm->pos += PAGE_SIZE;
+
+ return 1;
+}
+
int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
{
if (cprm->to_skip) {
@@ -863,7 +895,6 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
for (addr = start; addr < start + len; addr += PAGE_SIZE) {
struct page *page;
- int stop;
/*
* To avoid having to allocate page tables for virtual address
@@ -874,10 +905,7 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
*/
page = get_dump_page(addr);
if (page) {
- void *kaddr = kmap_local_page(page);
-
- stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
- kunmap_local(kaddr);
+ int stop = !dump_emit_page(cprm, page);
put_page(page);
if (stop)
return 0;
diff --git a/fs/internal.h b/fs/internal.h
index 87e96b9024ce..3e206d3e317c 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -16,6 +16,7 @@ struct shrink_control;
struct fs_context;
struct user_namespace;
struct pipe_inode_info;
+struct iov_iter;
/*
* block/bdev.c
@@ -221,3 +222,5 @@ ssize_t do_getxattr(struct user_namespace *mnt_userns,
int setxattr_copy(const char __user *name, struct xattr_ctx *ctx);
int do_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
struct xattr_ctx *ctx);
+
+ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos);
diff --git a/fs/read_write.c b/fs/read_write.c
index 1a261dcf1778..328ce8cf9a85 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -496,14 +496,9 @@ static ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t
}
/* caller is responsible for file_start_write/file_end_write */
-ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos)
+ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos)
{
- struct kvec iov = {
- .iov_base = (void *)buf,
- .iov_len = min_t(size_t, count, MAX_RW_COUNT),
- };
struct kiocb kiocb;
- struct iov_iter iter;
ssize_t ret;
if (WARN_ON_ONCE(!(file->f_mode & FMODE_WRITE)))
@@ -519,8 +514,7 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
init_sync_kiocb(&kiocb, file);
kiocb.ki_pos = pos ? *pos : 0;
- iov_iter_kvec(&iter, WRITE, &iov, 1, iov.iov_len);
- ret = file->f_op->write_iter(&kiocb, &iter);
+ ret = file->f_op->write_iter(&kiocb, from);
if (ret > 0) {
if (pos)
*pos = kiocb.ki_pos;
@@ -530,6 +524,18 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
inc_syscw(current);
return ret;
}
+
+/* caller is responsible for file_start_write/file_end_write */
+ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos)
+{
+ struct kvec iov = {
+ .iov_base = (void *)buf,
+ .iov_len = min_t(size_t, count, MAX_RW_COUNT),
+ };
+ struct iov_iter iter;
+ iov_iter_kvec(&iter, WRITE, &iov, 1, iov.iov_len);
+ return __kernel_write_iter(file, &iter, pos);
+}
/*
* This "EXPORT_SYMBOL_GPL()" is more of a "EXPORT_SYMBOL_DONTUSE()",
* but autofs is one of the few internal kernel users that actually
On Wed, Sep 28, 2022 at 07:29:43PM +0100, Al Viro wrote:
> On Tue, Sep 27, 2022 at 11:51:17PM +0100, Al Viro wrote:
> > [I'm going to send a pull request tomorrow if nobody yells;
> > please review and test - it seems to work fine here, but extra
> > eyes and extra testing would be very welcome]
>
> ... and now with page leak fixed:
>
> commit 06bbaa6dc53cb72040db952053432541acb9adc7
> Author: Al Viro <[email protected]>
> Date: Mon Sep 26 11:59:14 2022 -0400
>
> [coredump] don't use __kernel_write() on kmap_local_page()
>
> passing kmap_local_page() result to __kernel_write() is unsafe -
> random ->write_iter() might (and 9p one does) get unhappy when
> passed ITER_KVEC with pointer that came from kmap_local_page().
>
> Fix by providing a variant of __kernel_write() that takes an iov_iter
> from caller (__kernel_write() becomes a trivial wrapper) and adding
> dump_emit_page() that parallels dump_emit(), except that instead of
> __kernel_write() it uses __kernel_write_iter() with ITER_BVEC source.
>
> Fixes: 3159ed57792b "fs/coredump: use kmap_local_page()"
> Signed-off-by: Al Viro <[email protected]>
Reviewed-by: Ira Weiny <[email protected]>
Tested-by: Ira Weiny <[email protected]>
>
> diff --git a/fs/coredump.c b/fs/coredump.c
> index 9f4aae202109..1ab4f5b76a1e 100644
> --- a/fs/coredump.c
> +++ b/fs/coredump.c
> @@ -832,6 +832,38 @@ static int __dump_skip(struct coredump_params *cprm, size_t nr)
> }
> }
>
> +static int dump_emit_page(struct coredump_params *cprm, struct page *page)
> +{
> + struct bio_vec bvec = {
> + .bv_page = page,
> + .bv_offset = 0,
> + .bv_len = PAGE_SIZE,
> + };
> + struct iov_iter iter;
> + struct file *file = cprm->file;
> + loff_t pos = file->f_pos;
> + ssize_t n;
> +
> + if (cprm->to_skip) {
> + if (!__dump_skip(cprm, cprm->to_skip))
> + return 0;
> + cprm->to_skip = 0;
> + }
> + if (cprm->written + PAGE_SIZE > cprm->limit)
> + return 0;
> + if (dump_interrupted())
> + return 0;
> + iov_iter_bvec(&iter, WRITE, &bvec, 1, PAGE_SIZE);
> + n = __kernel_write_iter(cprm->file, &iter, &pos);
> + if (n != PAGE_SIZE)
> + return 0;
> + file->f_pos = pos;
> + cprm->written += PAGE_SIZE;
> + cprm->pos += PAGE_SIZE;
> +
> + return 1;
> +}
> +
> int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
> {
> if (cprm->to_skip) {
> @@ -863,7 +895,6 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
>
> for (addr = start; addr < start + len; addr += PAGE_SIZE) {
> struct page *page;
> - int stop;
>
> /*
> * To avoid having to allocate page tables for virtual address
> @@ -874,10 +905,7 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
> */
> page = get_dump_page(addr);
> if (page) {
> - void *kaddr = kmap_local_page(page);
> -
> - stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
> - kunmap_local(kaddr);
> + int stop = !dump_emit_page(cprm, page);
> put_page(page);
> if (stop)
> return 0;
> diff --git a/fs/internal.h b/fs/internal.h
> index 87e96b9024ce..3e206d3e317c 100644
> --- a/fs/internal.h
> +++ b/fs/internal.h
> @@ -16,6 +16,7 @@ struct shrink_control;
> struct fs_context;
> struct user_namespace;
> struct pipe_inode_info;
> +struct iov_iter;
>
> /*
> * block/bdev.c
> @@ -221,3 +222,5 @@ ssize_t do_getxattr(struct user_namespace *mnt_userns,
> int setxattr_copy(const char __user *name, struct xattr_ctx *ctx);
> int do_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
> struct xattr_ctx *ctx);
> +
> +ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos);
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 1a261dcf1778..328ce8cf9a85 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -496,14 +496,9 @@ static ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t
> }
>
> /* caller is responsible for file_start_write/file_end_write */
> -ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos)
> +ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos)
> {
> - struct kvec iov = {
> - .iov_base = (void *)buf,
> - .iov_len = min_t(size_t, count, MAX_RW_COUNT),
> - };
> struct kiocb kiocb;
> - struct iov_iter iter;
> ssize_t ret;
>
> if (WARN_ON_ONCE(!(file->f_mode & FMODE_WRITE)))
> @@ -519,8 +514,7 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
>
> init_sync_kiocb(&kiocb, file);
> kiocb.ki_pos = pos ? *pos : 0;
> - iov_iter_kvec(&iter, WRITE, &iov, 1, iov.iov_len);
> - ret = file->f_op->write_iter(&kiocb, &iter);
> + ret = file->f_op->write_iter(&kiocb, from);
> if (ret > 0) {
> if (pos)
> *pos = kiocb.ki_pos;
> @@ -530,6 +524,18 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
> inc_syscw(current);
> return ret;
> }
> +
> +/* caller is responsible for file_start_write/file_end_write */
> +ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos)
> +{
> + struct kvec iov = {
> + .iov_base = (void *)buf,
> + .iov_len = min_t(size_t, count, MAX_RW_COUNT),
> + };
> + struct iov_iter iter;
> + iov_iter_kvec(&iter, WRITE, &iov, 1, iov.iov_len);
> + return __kernel_write_iter(file, &iter, pos);
> +}
> /*
> * This "EXPORT_SYMBOL_GPL()" is more of a "EXPORT_SYMBOL_DONTUSE()",
> * but autofs is one of the few internal kernel users that actually
>
Ira Weiny:
> On Wed, Sep 28, 2022 at 07:29:43PM +0100, Al Viro wrote:
> > On Tue, Sep 27, 2022 at 11:51:17PM +0100, Al Viro wrote:
> > > [I'm going to send a pull request tomorrow if nobody yells;
> > > please review and test - it seems to work fine here, but extra
> > > eyes and extra testing would be very welcome]
I tried gdb backtrace 'bt' command with the new core by v6.0, and it
doesn't show the call trace correctly. Is it related to this commit?
test program
----------------------------------------
void f(int n)
{
printf("%d\n", n);
if (!n)
kill(getpid(), SIGQUIT);
f(--n);
}
int main(int argc, char *argv[])
{
f(atoi(argv[1]));
return 0;
}
----------------------------------------
ulimit -c unlimited
coredump 2
gdb coredump core
bt
----------------------------------------
expected result
kill
f
f
f
main
----------------------------------------
actual result
??
??
----------------------------------------
J. R. Okajima
On Mon, Oct 03, 2022 at 07:48:28PM +0900, J. R. Okajima wrote:
> Ira Weiny:
> > On Wed, Sep 28, 2022 at 07:29:43PM +0100, Al Viro wrote:
> > > On Tue, Sep 27, 2022 at 11:51:17PM +0100, Al Viro wrote:
> > > > [I'm going to send a pull request tomorrow if nobody yells;
> > > > please review and test - it seems to work fine here, but extra
> > > > eyes and extra testing would be very welcome]
>
> I tried gdb backtrace 'bt' command with the new core by v6.0, and it
> doesn't show the call trace correctly. Is it related to this commit?
>
Are you also getting something like this?
BFD: warning: /mnt/9p/test-okajima/core is truncated: expected core file size >= 225280, found: 76616
I did not see that before. I'm running through this patch vs a fix to
kmap_to_page()[1] and I may have gotten the 2 crossed up. So I'm retesting
with your test below.
Ira
[1] https://lore.kernel.org/linux-mm/[email protected]/
> test program
> ----------------------------------------
> void f(int n)
> {
> printf("%d\n", n);
> if (!n)
> kill(getpid(), SIGQUIT);
> f(--n);
> }
>
> int main(int argc, char *argv[])
> {
> f(atoi(argv[1]));
> return 0;
> }
> ----------------------------------------
> ulimit -c unlimited
> coredump 2
> gdb coredump core
> bt
> ----------------------------------------
> expected result
> kill
> f
> f
> f
> main
> ----------------------------------------
> actual result
> ??
> ??
> ----------------------------------------
>
>
> J. R. Okajima
On Mon, Oct 03, 2022 at 12:31:36PM -0700, Ira Weiny wrote:
> On Mon, Oct 03, 2022 at 07:48:28PM +0900, J. R. Okajima wrote:
> > Ira Weiny:
> > > On Wed, Sep 28, 2022 at 07:29:43PM +0100, Al Viro wrote:
> > > > On Tue, Sep 27, 2022 at 11:51:17PM +0100, Al Viro wrote:
> > > > > [I'm going to send a pull request tomorrow if nobody yells;
> > > > > please review and test - it seems to work fine here, but extra
> > > > > eyes and extra testing would be very welcome]
> >
> > I tried gdb backtrace 'bt' command with the new core by v6.0, and it
> > doesn't show the call trace correctly. Is it related to this commit?
> >
>
> Are you also getting something like this?
>
> BFD: warning: /mnt/9p/test-okajima/core is truncated: expected core file size >= 225280, found: 76616
>
> I did not see that before. I'm running through this patch vs a fix to
> kmap_to_page()[1] and I may have gotten the 2 crossed up. So I'm retesting
> with your test below.
Argh.... Try this:
fix coredump breakage caused by badly tested "[coredump] don't use __kernel_write() on kmap_local_page()"
Let me count the ways I'd screwed up:
* when emitting a page, handling of gaps in coredump should happen
before fetching the current file position.
* fix for problem that occurs on rather uncommon setups (and hadn't
been observed in the wild) sent very late in the cycle.
* ... with badly insufficient testing, introducing an easily
reproducable breakage. Without giving it time to soak in -next.
Fucked-up-by: Al Viro <[email protected]>
Fixes: 06bbaa6dc53c "[coredump] don't use __kernel_write() on kmap_local_page()"
Signed-off-by: Al Viro <[email protected]>
---
diff --git a/fs/coredump.c b/fs/coredump.c
index 1ab4f5b76a1e..3538f3a63965 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -841,7 +841,7 @@ static int dump_emit_page(struct coredump_params *cprm, struct page *page)
};
struct iov_iter iter;
struct file *file = cprm->file;
- loff_t pos = file->f_pos;
+ loff_t pos;
ssize_t n;
if (cprm->to_skip) {
@@ -853,6 +853,7 @@ static int dump_emit_page(struct coredump_params *cprm, struct page *page)
return 0;
if (dump_interrupted())
return 0;
+ pos = file->f_pos;
iov_iter_bvec(&iter, WRITE, &bvec, 1, PAGE_SIZE);
n = __kernel_write_iter(cprm->file, &iter, &pos);
if (n != PAGE_SIZE)
Al Viro:
> Argh.... Try this:
>
> fix coredump breakage caused by badly tested "[coredump] don't use __kernel_write() on kmap_local_page()"
Thanx, it passed my local test.
> * fix for problem that occurs on rather uncommon setups (and hadn't
> been observed in the wild) sent very late in the cycle.
If the commit was merged in RC versions, I guess someone found the
problem earlier.
J. R. Okajima
On Tue, Oct 04, 2022 at 07:58:14AM +0900, J. R. Okajima wrote:
> Al Viro:
> > Argh.... Try this:
> >
> > fix coredump breakage caused by badly tested "[coredump] don't use __kernel_write() on kmap_local_page()"
>
> Thanx, it passed my local test.
>
>
> > * fix for problem that occurs on rather uncommon setups (and hadn't
> > been observed in the wild) sent very late in the cycle.
>
> If the commit was merged in RC versions, I guess someone found the
> problem earlier.
Most likely - the breakage is really not hard to trigger ;-/
Linus, which way would you prefer to handle that? It's
a brown paperbag stuff - the worst I had in quite a while.
Mea maxima culpa ;-/
One variant would be to revert the original patch, put its
(hopefully) fixed variant into -next and let it sit there for
a while. Another is to put this incremental into -next and
merge it into mainline once it gets a sane amount of testing.
Up to you...
On Mon, Oct 3, 2022 at 5:31 PM Al Viro <[email protected]> wrote:
>
> OK, incremental is in #fixes, pushed out.
I'm assuming I'll still get a proper pull request. No?
Linus
On Mon, Oct 3, 2022 at 4:37 PM Al Viro <[email protected]> wrote:
>
> One variant would be to revert the original patch, put its
> (hopefully) fixed variant into -next and let it sit there for
> a while. Another is to put this incremental into -next and
> merge it into mainline once it gets a sane amount of testing.
Just do the incremental fix. It looks obvious enough ("oops, we need
to get the pos _after_ we've done any skip-lseeks on the core file")
that I think it would be just harder to follow a "revert and follow up
with a fix".
I don't think it needs a ton of extra testing, with Okajima having
already confirmed it fixes his problem case..
Linus
On Mon, Oct 03, 2022 at 05:20:03PM -0700, Linus Torvalds wrote:
> On Mon, Oct 3, 2022 at 4:37 PM Al Viro <[email protected]> wrote:
> >
> > One variant would be to revert the original patch, put its
> > (hopefully) fixed variant into -next and let it sit there for
> > a while. Another is to put this incremental into -next and
> > merge it into mainline once it gets a sane amount of testing.
>
> Just do the incremental fix. It looks obvious enough ("oops, we need
> to get the pos _after_ we've done any skip-lseeks on the core file")
> that I think it would be just harder to follow a "revert and follow up
> with a fix".
>
> I don't think it needs a ton of extra testing, with Okajima having
> already confirmed it fixes his problem case..
OK, incremental is in #fixes, pushed out.
On Mon, Oct 03, 2022 at 05:37:24PM -0700, Linus Torvalds wrote:
> On Mon, Oct 3, 2022 at 5:31 PM Al Viro <[email protected]> wrote:
> >
> > OK, incremental is in #fixes, pushed out.
>
> I'm assuming I'll still get a proper pull request. No?
Pull request follows; after all, whatever else is there, this is an obvious
fix for the breakage Okajima caught...
Al, very much hoping there's no other embarrassing fuckups lurking in that
thing ;-/
The following changes since commit 4fe89d07dcc2804c8b562f6c7896a45643d34b2f:
Linux 6.0 (2022-10-02 14:09:07 -0700)
are available in the Git repository at:
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git tags/pull-fixes
for you to fetch changes up to 4f526fef91b24197d489ff86789744c67f475bb4:
[brown paperbag] fix coredump breakage (2022-10-03 20:28:38 -0400)
----------------------------------------------------------------
fs/coredump fix
----------------------------------------------------------------
Al Viro (1):
[brown paperbag] fix coredump breakage
fs/coredump.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
On Tue, Oct 04, 2022 at 07:58:14AM +0900, J. R. Okajima wrote:
> Al Viro:
> > Argh.... Try this:
> >
> > fix coredump breakage caused by badly tested "[coredump] don't use __kernel_write() on kmap_local_page()"
>
> Thanx, it passed my local test.
My mess up too. I thought I had tested this when I had tested the
kmap_to_page() fix.
:-(
This works for me too now that I have my git trees straight.
Sorry.
Ira
>
>
> > * fix for problem that occurs on rather uncommon setups (and hadn't
> > been observed in the wild) sent very late in the cycle.
>
> If the commit was merged in RC versions, I guess someone found the
> problem earlier.
>
>
> J. R. Okajima
On Tue, Oct 4, 2022 at 2:51 AM Linus Torvalds
<[email protected]> wrote:
>
> On Mon, Oct 3, 2022 at 4:37 PM Al Viro <[email protected]> wrote:
> >
> > One variant would be to revert the original patch, put its
> > (hopefully) fixed variant into -next and let it sit there for
> > a while. Another is to put this incremental into -next and
> > merge it into mainline once it gets a sane amount of testing.
>
> Just do the incremental fix. It looks obvious enough ("oops, we need
> to get the pos _after_ we've done any skip-lseeks on the core file")
> that I think it would be just harder to follow a "revert and follow up
> with a fix".
>
> I don't think it needs a ton of extra testing, with Okajima having
> already confirmed it fixes his problem case..
>
> Linus
[ CC Geert ]
There was another patch from Geert concerning the same coredump changes:
[PATCH] coredump: Move dump_emit_page() to kill unused warning
If CONFIG_ELF_CORE is not set:
fs/coredump.c:835:12: error: ‘dump_emit_page’ defined but not used
[-Werror=unused-function]
835 | static int dump_emit_page(struct coredump_params *cprm,
struct page *page)
| ^~~~~~~~~~~~~~
Fix this by moving dump_emit_page() inside the existing section
protected by #ifdef CONFIG_ELF_CORE.
Fixes: 06bbaa6dc53cb720 ("[coredump] don't use __kernel_write() on
kmap_local_page()")
Signed-off-by: Geert Uytterhoeven <[email protected]>
Please, check yourself!
Best regards,
-Sedat-
[1] https://lore.kernel.org/all/[email protected]/
On Tue, Oct 4, 2022 at 8:18 AM Sedat Dilek <[email protected]> wrote:
>
> On Tue, Oct 4, 2022 at 2:51 AM Linus Torvalds
> <[email protected]> wrote:
> >
> > On Mon, Oct 3, 2022 at 4:37 PM Al Viro <[email protected]> wrote:
> > >
> > > One variant would be to revert the original patch, put its
> > > (hopefully) fixed variant into -next and let it sit there for
> > > a while. Another is to put this incremental into -next and
> > > merge it into mainline once it gets a sane amount of testing.
> >
> > Just do the incremental fix. It looks obvious enough ("oops, we need
> > to get the pos _after_ we've done any skip-lseeks on the core file")
> > that I think it would be just harder to follow a "revert and follow up
> > with a fix".
> >
> > I don't think it needs a ton of extra testing, with Okajima having
> > already confirmed it fixes his problem case..
> >
> > Linus
>
> [ CC Geert ]
>
> There was another patch from Geert concerning the same coredump changes:
>
> [PATCH] coredump: Move dump_emit_page() to kill unused warning
>
> If CONFIG_ELF_CORE is not set:
>
> fs/coredump.c:835:12: error: ‘dump_emit_page’ defined but not used
> [-Werror=unused-function]
> 835 | static int dump_emit_page(struct coredump_params *cprm,
> struct page *page)
> | ^~~~~~~~~~~~~~
>
> Fix this by moving dump_emit_page() inside the existing section
> protected by #ifdef CONFIG_ELF_CORE.
>
> Fixes: 06bbaa6dc53cb720 ("[coredump] don't use __kernel_write() on
> kmap_local_page()")
> Signed-off-by: Geert Uytterhoeven <[email protected]>
>
> Please, check yourself!
>
> Best regards,
> -Sedat-
>
> [1] https://lore.kernel.org/all/[email protected]/
[ CC Ren Zhijie <[email protected]> ]
Looks like the same patch as of Geert.
-Sedat-
[1] https://lore.kernel.org/all/[email protected]/
Hi Al,
On Tue, Oct 4, 2022 at 8:19 AM Sedat Dilek <[email protected]> wrote:
> On Tue, Oct 4, 2022 at 2:51 AM Linus Torvalds
> <[email protected]> wrote:
> > On Mon, Oct 3, 2022 at 4:37 PM Al Viro <[email protected]> wrote:
> > >
> > > One variant would be to revert the original patch, put its
> > > (hopefully) fixed variant into -next and let it sit there for
> > > a while. Another is to put this incremental into -next and
> > > merge it into mainline once it gets a sane amount of testing.
> >
> > Just do the incremental fix. It looks obvious enough ("oops, we need
> > to get the pos _after_ we've done any skip-lseeks on the core file")
> > that I think it would be just harder to follow a "revert and follow up
> > with a fix".
> >
> > I don't think it needs a ton of extra testing, with Okajima having
> > already confirmed it fixes his problem case..
> >
> > Linus
>
> [ CC Geert ]
>
> There was another patch from Geert concerning the same coredump changes:
>
> [PATCH] coredump: Move dump_emit_page() to kill unused warning
>
> If CONFIG_ELF_CORE is not set:
>
> fs/coredump.c:835:12: error: ‘dump_emit_page’ defined but not used
> [-Werror=unused-function]
> 835 | static int dump_emit_page(struct coredump_params *cprm,
> struct page *page)
> | ^~~~~~~~~~~~~~
>
> Fix this by moving dump_emit_page() inside the existing section
> protected by #ifdef CONFIG_ELF_CORE.
>
> Fixes: 06bbaa6dc53cb720 ("[coredump] don't use __kernel_write() on
> kmap_local_page()")
> Signed-off-by: Geert Uytterhoeven <[email protected]>
>
> Please, check yourself!
The build issue is still present in today's linux-next.
Al, can you please apply my fix, so Greg can backport all of this to stable?
https://lore.kernel.org/all/[email protected]
Thanks!
> [1] https://lore.kernel.org/all/[email protected]/
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds