2018-02-05 20:01:41

by Jin Qian

Subject: [PATCH 1/1] ext4: don't put symlink in pagecache into highmem

From: Jin Qian <[email protected]>

partial backport of 21fc61c73c3903c4c312d0802da01ec2b323d174.

ext4_encrypted_follow_link uses kmap() for cpage
caddr = kmap(cpage);

_ext4_fname_disk_to_usr calls virt_to_page on the kmapped address.
_ext4_fname_disk_to_usr()
ext4_fname_decrypt()
sg_init_one()
sg_init_one(&src_sg, iname->name, iname->len);
sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));

Cc: [email protected]
Signed-off-by: Al Viro <[email protected]>
Signed-off-by: Jin Qian <[email protected]>
---
fs/ext4/inode.c | 1 +
fs/ext4/namei.c | 1 +
fs/ext4/symlink.c | 10 +++-------
fs/inode.c | 6 ++++++
include/linux/fs.h | 1 +
5 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 4df1cb19a243..f0cabc8c96cb 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4417,6 +4417,7 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
inode->i_op = &ext4_symlink_inode_operations;
ext4_set_aops(inode);
}
+ inode_nohighmem(inode);
} else if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode) ||
S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
inode->i_op = &ext4_special_inode_operations;
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 4c36dca486cc..32960b3ecd4f 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -3151,6 +3151,7 @@ static int ext4_symlink(struct inode *dir,
if ((disk_link.len > EXT4_N_BLOCKS * 4)) {
if (!encryption_required)
inode->i_op = &ext4_symlink_inode_operations;
+ inode_nohighmem(inode);
ext4_set_aops(inode);
/*
* We cannot call page_symlink() with transaction started
diff --git a/fs/ext4/symlink.c b/fs/ext4/symlink.c
index e8e7af62ac95..287c3980fa0b 100644
--- a/fs/ext4/symlink.c
+++ b/fs/ext4/symlink.c
@@ -45,7 +45,7 @@ static const char *ext4_encrypted_follow_link(struct dentry *dentry, void **cook
cpage = read_mapping_page(inode->i_mapping, 0, NULL);
if (IS_ERR(cpage))
return ERR_CAST(cpage);
- caddr = kmap(cpage);
+ caddr = page_address(cpage);
caddr[size] = 0;
}

@@ -75,16 +75,12 @@ static const char *ext4_encrypted_follow_link(struct dentry *dentry, void **cook
/* Null-terminate the name */
if (res <= plen)
paddr[res] = '\0';
- if (cpage) {
- kunmap(cpage);
+ if (cpage)
page_cache_release(cpage);
- }
return *cookie = paddr;
errout:
- if (cpage) {
- kunmap(cpage);
+ if (cpage)
page_cache_release(cpage);
- }
kfree(paddr);
return ERR_PTR(res);
}
diff --git a/fs/inode.c b/fs/inode.c
index b0edef500590..b95615f3fc50 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2028,3 +2028,9 @@ void inode_set_flags(struct inode *inode, unsigned int flags,
new_flags) != old_flags));
}
EXPORT_SYMBOL(inode_set_flags);
+
+void inode_nohighmem(struct inode *inode)
+{
+ mapping_set_gfp_mask(inode->i_mapping, GFP_USER);
+}
+EXPORT_SYMBOL(inode_nohighmem);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index c8decb7075d6..f746a59fcc88 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3066,5 +3066,6 @@ static inline bool dir_relax(struct inode *inode)
}

extern bool path_noexec(const struct path *path);
+extern void inode_nohighmem(struct inode *inode);

#endif /* _LINUX_FS_H */
--
2.16.0.rc1.238.g530d649a79-goog

2018-02-06 13:34:27

by Theodore Ts'o

Subject: Re: [PATCH 1/1] ext4: don't put symlink in pagecache into highmem

On Mon, Feb 05, 2018 at 11:57:39AM -0800, Jin Qian wrote:
> From: Jin Qian <[email protected]>
>
> partial backport of 21fc61c73c3903c4c312d0802da01ec2b323d174.

Hi Jin,

When you do a partial backport like this, it would be helpful you
could indicate which kernel version(s) it is meant for, since there
are many stable kernel trees.

Thanks!!

- Ted