Hello,
syzbot found the following crash on:
HEAD commit: 8bbbc5cf kmsan: don't compile memmove
git tree: https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=14394265e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=cd0e9a6b0e555cc3
dashboard link: https://syzkaller.appspot.com/bug?extid=fcab69d1ada3e8d6f06b
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1338127ee00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=161403ede00000
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email protected]
=====================================================
BUG: KMSAN: uninit-value in strlen+0x5e/0xa0 lib/string.c:552
CPU: 1 PID: 11402 Comm: syz-executor230 Not tainted 5.6.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c9/0x220 lib/dump_stack.c:118
kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118
__msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
strlen+0x5e/0xa0 lib/string.c:552
simple_attr_read+0x1ec/0x740 fs/libfs.c:935
debugfs_attr_read+0x13e/0x290 fs/debugfs/file.c:360
__vfs_read+0x1a9/0xc80 fs/read_write.c:425
vfs_read+0x346/0x6a0 fs/read_write.c:461
ksys_read+0x267/0x450 fs/read_write.c:587
__do_sys_read fs/read_write.c:597 [inline]
__se_sys_read+0x92/0xb0 fs/read_write.c:595
__x64_sys_read+0x4a/0x70 fs/read_write.c:595
do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x440269
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff09d3bc68 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440269
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00000000006ca018 R08: 000000000000000a R09: 000000000000000a
R10: 0000000000010001 R11: 0000000000000246 R12: 0000000000401af0
R13: 0000000000401b80 R14: 0000000000000000 R15: 0000000000000000
Uninit was created at:
kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
kmsan_internal_poison_shadow+0x66/0xd0 mm/kmsan/kmsan.c:127
kmsan_slab_alloc+0x8a/0xe0 mm/kmsan/kmsan_hooks.c:82
slab_alloc_node mm/slub.c:2793 [inline]
slab_alloc mm/slub.c:2802 [inline]
kmem_cache_alloc_trace+0x6f3/0xd70 mm/slub.c:2819
kmalloc include/linux/slab.h:555 [inline]
simple_attr_open+0xd4/0x400 fs/libfs.c:894
lowpan_enable_fops_open+0x94/0xb0 net/bluetooth/6lowpan.c:1105
open_proxy_open+0x657/0x800 fs/debugfs/file.c:189
do_dentry_open+0xf89/0x1820 fs/open.c:797
vfs_open+0xaf/0xe0 fs/open.c:914
do_last fs/namei.c:3490 [inline]
path_openat+0x4d57/0x6bd0 fs/namei.c:3607
do_filp_open+0x2b8/0x710 fs/namei.c:3637
do_sys_openat2+0x92e/0xd40 fs/open.c:1149
do_sys_open fs/open.c:1165 [inline]
__do_sys_openat fs/open.c:1179 [inline]
__se_sys_openat+0x24a/0x2b0 fs/open.c:1174
__x64_sys_openat+0x56/0x70 fs/open.c:1174
do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x44/0xa9
=====================================================
---
This bug is generated by a bot. It may contain errors.
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On Thu, Feb 27, 2020 at 10:29 AM syzbot
<[email protected]> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 8bbbc5cf kmsan: don't compile memmove
> git tree: https://github.com/google/kmsan.git master
> console output: https://syzkaller.appspot.com/x/log.txt?x=14394265e00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=cd0e9a6b0e555cc3
> dashboard link: https://syzkaller.appspot.com/bug?extid=fcab69d1ada3e8d6f06b
> compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1338127ee00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=161403ede00000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: [email protected]
This report says it's uninit in strlen, but there's actually an
information leak later on that lets the user read arbitrary data past
the non-terminated attr->get_buf.
Hi Greg, Rafael, Arnd,
> This report says it's uninit in strlen, but there's actually an
> information leak later on that lets the user read arbitrary data past
> the non-terminated attr->get_buf.
The attached PoC demonstrates the problem.
I am not sure how bad is that, given that /sys/kernel/debug is usually
accessible only to the root, and simple attribute files don't seem to
be used anywhere else.
From: Eric Biggers <[email protected]>
Reading from a debugfs file at a nonzero position, without first reading
at position 0, leaks uninitialized memory to userspace.
It's a bit tricky to do this, since lseek() and pread() aren't allowed
on these files, and write() doesn't update the position on them. But
writing to them with splice() *does* update the position:
#define _GNU_SOURCE 1
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
int main()
{
int pipes[2], fd, n, i;
char buf[32];
pipe(pipes);
write(pipes[1], "0", 1);
fd = open("/sys/kernel/debug/fault_around_bytes", O_RDWR);
splice(pipes[0], NULL, fd, NULL, 1, 0);
n = read(fd, buf, sizeof(buf));
for (i = 0; i < n; i++)
printf("%02x", buf[i]);
printf("\n");
}
Output:
5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a30
Fix the infoleak by making simple_attr_read() always fill
simple_attr::get_buf if it hasn't been filled yet.
Reported-by: [email protected]
Reported-by: Alexander Potapenko <[email protected]>
Fixes: acaefc25d21f ("[PATCH] libfs: add simple attribute files")
Cc: [email protected]
Signed-off-by: Eric Biggers <[email protected]>
---
fs/libfs.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/fs/libfs.c b/fs/libfs.c
index c686bd9caac6..3759fbacf522 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -891,7 +891,7 @@ int simple_attr_open(struct inode *inode, struct file *file,
{
struct simple_attr *attr;
- attr = kmalloc(sizeof(*attr), GFP_KERNEL);
+ attr = kzalloc(sizeof(*attr), GFP_KERNEL);
if (!attr)
return -ENOMEM;
@@ -931,9 +931,11 @@ ssize_t simple_attr_read(struct file *file, char __user *buf,
if (ret)
return ret;
- if (*ppos) { /* continued read */
+ if (*ppos && attr->get_buf[0]) {
+ /* continued read */
size = strlen(attr->get_buf);
- } else { /* first read */
+ } else {
+ /* first read */
u64 val;
ret = attr->get(attr->data, &val);
if (ret)
--
2.25.1
On Sat, Mar 07, 2020 at 06:38:49PM -0800, Eric Biggers wrote:
> From: Eric Biggers <[email protected]>
>
> Reading from a debugfs file at a nonzero position, without first reading
> at position 0, leaks uninitialized memory to userspace.
>
> It's a bit tricky to do this, since lseek() and pread() aren't allowed
> on these files, and write() doesn't update the position on them. But
> writing to them with splice() *does* update the position:
>
> #define _GNU_SOURCE 1
> #include <fcntl.h>
> #include <stdio.h>
> #include <unistd.h>
> int main()
> {
> int pipes[2], fd, n, i;
> char buf[32];
>
> pipe(pipes);
> write(pipes[1], "0", 1);
> fd = open("/sys/kernel/debug/fault_around_bytes", O_RDWR);
> splice(pipes[0], NULL, fd, NULL, 1, 0);
> n = read(fd, buf, sizeof(buf));
> for (i = 0; i < n; i++)
> printf("%02x", buf[i]);
> printf("\n");
> }
>
> Output:
> 5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a30
>
> Fix the infoleak by making simple_attr_read() always fill
> simple_attr::get_buf if it hasn't been filled yet.
>
> Reported-by: [email protected]
> Reported-by: Alexander Potapenko <[email protected]>
> Fixes: acaefc25d21f ("[PATCH] libfs: add simple attribute files")
> Cc: [email protected]
> Signed-off-by: Eric Biggers <[email protected]>
> ---
> fs/libfs.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/libfs.c b/fs/libfs.c
> index c686bd9caac6..3759fbacf522 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -891,7 +891,7 @@ int simple_attr_open(struct inode *inode, struct file *file,
> {
> struct simple_attr *attr;
>
> - attr = kmalloc(sizeof(*attr), GFP_KERNEL);
> + attr = kzalloc(sizeof(*attr), GFP_KERNEL);
> if (!attr)
> return -ENOMEM;
>
> @@ -931,9 +931,11 @@ ssize_t simple_attr_read(struct file *file, char __user *buf,
> if (ret)
> return ret;
>
> - if (*ppos) { /* continued read */
> + if (*ppos && attr->get_buf[0]) {
> + /* continued read */
> size = strlen(attr->get_buf);
> - } else { /* first read */
> + } else {
> + /* first read */
> u64 val;
> ret = attr->get(attr->data, &val);
> if (ret)
> --
> 2.25.1
Any comments on this? Al, seems this is something you should pick up?
- Eric
On Fri, Mar 13, 2020 at 09:45:11AM -0700, Eric Biggers wrote:
> On Sat, Mar 07, 2020 at 06:38:49PM -0800, Eric Biggers wrote:
> > From: Eric Biggers <[email protected]>
> >
> > Reading from a debugfs file at a nonzero position, without first reading
> > at position 0, leaks uninitialized memory to userspace.
> >
> > It's a bit tricky to do this, since lseek() and pread() aren't allowed
> > on these files, and write() doesn't update the position on them. But
> > writing to them with splice() *does* update the position:
> >
> > #define _GNU_SOURCE 1
> > #include <fcntl.h>
> > #include <stdio.h>
> > #include <unistd.h>
> > int main()
> > {
> > int pipes[2], fd, n, i;
> > char buf[32];
> >
> > pipe(pipes);
> > write(pipes[1], "0", 1);
> > fd = open("/sys/kernel/debug/fault_around_bytes", O_RDWR);
> > splice(pipes[0], NULL, fd, NULL, 1, 0);
> > n = read(fd, buf, sizeof(buf));
> > for (i = 0; i < n; i++)
> > printf("%02x", buf[i]);
> > printf("\n");
> > }
> >
> > Output:
> > 5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a30
> >
> > Fix the infoleak by making simple_attr_read() always fill
> > simple_attr::get_buf if it hasn't been filled yet.
> >
> > Reported-by: [email protected]
> > Reported-by: Alexander Potapenko <[email protected]>
> > Fixes: acaefc25d21f ("[PATCH] libfs: add simple attribute files")
> > Cc: [email protected]
> > Signed-off-by: Eric Biggers <[email protected]>
> > ---
> > fs/libfs.c | 8 +++++---
> > 1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/libfs.c b/fs/libfs.c
> > index c686bd9caac6..3759fbacf522 100644
> > --- a/fs/libfs.c
> > +++ b/fs/libfs.c
> > @@ -891,7 +891,7 @@ int simple_attr_open(struct inode *inode, struct file *file,
> > {
> > struct simple_attr *attr;
> >
> > - attr = kmalloc(sizeof(*attr), GFP_KERNEL);
> > + attr = kzalloc(sizeof(*attr), GFP_KERNEL);
> > if (!attr)
> > return -ENOMEM;
> >
> > @@ -931,9 +931,11 @@ ssize_t simple_attr_read(struct file *file, char __user *buf,
> > if (ret)
> > return ret;
> >
> > - if (*ppos) { /* continued read */
> > + if (*ppos && attr->get_buf[0]) {
> > + /* continued read */
> > size = strlen(attr->get_buf);
> > - } else { /* first read */
> > + } else {
> > + /* first read */
> > u64 val;
> > ret = attr->get(attr->data, &val);
> > if (ret)
> > --
> > 2.25.1
>
> Any comments on this? Al, seems this is something you should pick up?
>
> - Eric
Ping.
On Wed, Mar 18, 2020 at 09:39:40AM -0700, Eric Biggers wrote:
> On Fri, Mar 13, 2020 at 09:45:11AM -0700, Eric Biggers wrote:
> > On Sat, Mar 07, 2020 at 06:38:49PM -0800, Eric Biggers wrote:
> > > From: Eric Biggers <[email protected]>
> > >
> > > Reading from a debugfs file at a nonzero position, without first reading
> > > at position 0, leaks uninitialized memory to userspace.
> > >
> > > It's a bit tricky to do this, since lseek() and pread() aren't allowed
> > > on these files, and write() doesn't update the position on them. But
> > > writing to them with splice() *does* update the position:
> > >
> > > #define _GNU_SOURCE 1
> > > #include <fcntl.h>
> > > #include <stdio.h>
> > > #include <unistd.h>
> > > int main()
> > > {
> > > int pipes[2], fd, n, i;
> > > char buf[32];
> > >
> > > pipe(pipes);
> > > write(pipes[1], "0", 1);
> > > fd = open("/sys/kernel/debug/fault_around_bytes", O_RDWR);
> > > splice(pipes[0], NULL, fd, NULL, 1, 0);
> > > n = read(fd, buf, sizeof(buf));
> > > for (i = 0; i < n; i++)
> > > printf("%02x", buf[i]);
> > > printf("\n");
> > > }
> > >
> > > Output:
> > > 5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a30
> > >
> > > Fix the infoleak by making simple_attr_read() always fill
> > > simple_attr::get_buf if it hasn't been filled yet.
> > >
> > > Reported-by: [email protected]
> > > Reported-by: Alexander Potapenko <[email protected]>
> > > Fixes: acaefc25d21f ("[PATCH] libfs: add simple attribute files")
> > > Cc: [email protected]
> > > Signed-off-by: Eric Biggers <[email protected]>
> > > ---
> > > fs/libfs.c | 8 +++++---
> > > 1 file changed, 5 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/fs/libfs.c b/fs/libfs.c
> > > index c686bd9caac6..3759fbacf522 100644
> > > --- a/fs/libfs.c
> > > +++ b/fs/libfs.c
> > > @@ -891,7 +891,7 @@ int simple_attr_open(struct inode *inode, struct file *file,
> > > {
> > > struct simple_attr *attr;
> > >
> > > - attr = kmalloc(sizeof(*attr), GFP_KERNEL);
> > > + attr = kzalloc(sizeof(*attr), GFP_KERNEL);
> > > if (!attr)
> > > return -ENOMEM;
> > >
> > > @@ -931,9 +931,11 @@ ssize_t simple_attr_read(struct file *file, char __user *buf,
> > > if (ret)
> > > return ret;
> > >
> > > - if (*ppos) { /* continued read */
> > > + if (*ppos && attr->get_buf[0]) {
> > > + /* continued read */
> > > size = strlen(attr->get_buf);
> > > - } else { /* first read */
> > > + } else {
> > > + /* first read */
> > > u64 val;
> > > ret = attr->get(attr->data, &val);
> > > if (ret)
> > > --
> > > 2.25.1
> >
> > Any comments on this? Al, seems this is something you should pick up?
> >
> > - Eric
>
> Ping.
>
Andrew, can you consider taking this patch? Al has been ignoring it, and this
seems like a fairly important fix. This bug affects many (most?) debugfs files,
and it affects years old kernels too not just recent ones.
Thanks,
- Eric
On Sat, Mar 07, 2020 at 06:38:49PM -0800, Eric Biggers wrote:
> From: Eric Biggers <[email protected]>
>
> Reading from a debugfs file at a nonzero position, without first reading
> at position 0, leaks uninitialized memory to userspace.
>
> It's a bit tricky to do this, since lseek() and pread() aren't allowed
> on these files, and write() doesn't update the position on them. But
> writing to them with splice() *does* update the position:
>
> #define _GNU_SOURCE 1
> #include <fcntl.h>
> #include <stdio.h>
> #include <unistd.h>
> int main()
> {
> int pipes[2], fd, n, i;
> char buf[32];
>
> pipe(pipes);
> write(pipes[1], "0", 1);
> fd = open("/sys/kernel/debug/fault_around_bytes", O_RDWR);
> splice(pipes[0], NULL, fd, NULL, 1, 0);
> n = read(fd, buf, sizeof(buf));
> for (i = 0; i < n; i++)
> printf("%02x", buf[i]);
> printf("\n");
> }
>
> Output:
> 5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a30
>
> Fix the infoleak by making simple_attr_read() always fill
> simple_attr::get_buf if it hasn't been filled yet.
>
> Reported-by: [email protected]
> Reported-by: Alexander Potapenko <[email protected]>
> Fixes: acaefc25d21f ("[PATCH] libfs: add simple attribute files")
> Cc: [email protected]
> Signed-off-by: Eric Biggers <[email protected]>
Yikes, that's an important fix!
Acked-by: Kees Cook <[email protected]>
Luckily (as Alexander mentioned too), most distros make debugfs
non-accessible by non-root (I hope):
$ ls -lda /sys/kernel/debug
drwx------ 39 root root 0 Jan 8 09:10 /sys/kernel/debug/
That function is also exposed via DEFINE_SIMPLE_ATTRIBUTE(), but those
users appear to also be mostly (all?) debugfs too.
And, just to note, for v5.3 and later, this would be fully mitigated by
booting with "init_on_alloc=1".
-Kees
> ---
> fs/libfs.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/libfs.c b/fs/libfs.c
> index c686bd9caac6..3759fbacf522 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -891,7 +891,7 @@ int simple_attr_open(struct inode *inode, struct file *file,
> {
> struct simple_attr *attr;
>
> - attr = kmalloc(sizeof(*attr), GFP_KERNEL);
> + attr = kzalloc(sizeof(*attr), GFP_KERNEL);
> if (!attr)
> return -ENOMEM;
>
> @@ -931,9 +931,11 @@ ssize_t simple_attr_read(struct file *file, char __user *buf,
> if (ret)
> return ret;
>
> - if (*ppos) { /* continued read */
> + if (*ppos && attr->get_buf[0]) {
> + /* continued read */
> size = strlen(attr->get_buf);
> - } else { /* first read */
> + } else {
> + /* first read */
> u64 val;
> ret = attr->get(attr->data, &val);
> if (ret)
> --
> 2.25.1
>
--
Kees Cook
On Sat, Mar 21, 2020 at 08:56:20PM -0700, Eric Biggers wrote:
> On Wed, Mar 18, 2020 at 09:39:40AM -0700, Eric Biggers wrote:
> > On Fri, Mar 13, 2020 at 09:45:11AM -0700, Eric Biggers wrote:
> > > On Sat, Mar 07, 2020 at 06:38:49PM -0800, Eric Biggers wrote:
> > > > From: Eric Biggers <[email protected]>
> > > >
> > > > Reading from a debugfs file at a nonzero position, without first reading
> > > > at position 0, leaks uninitialized memory to userspace.
> > > >
> > > > It's a bit tricky to do this, since lseek() and pread() aren't allowed
> > > > on these files, and write() doesn't update the position on them. But
> > > > writing to them with splice() *does* update the position:
> > > >
> > > > #define _GNU_SOURCE 1
> > > > #include <fcntl.h>
> > > > #include <stdio.h>
> > > > #include <unistd.h>
> > > > int main()
> > > > {
> > > > int pipes[2], fd, n, i;
> > > > char buf[32];
> > > >
> > > > pipe(pipes);
> > > > write(pipes[1], "0", 1);
> > > > fd = open("/sys/kernel/debug/fault_around_bytes", O_RDWR);
> > > > splice(pipes[0], NULL, fd, NULL, 1, 0);
> > > > n = read(fd, buf, sizeof(buf));
> > > > for (i = 0; i < n; i++)
> > > > printf("%02x", buf[i]);
> > > > printf("\n");
> > > > }
> > > >
> > > > Output:
> > > > 5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a30
> > > >
> > > > Fix the infoleak by making simple_attr_read() always fill
> > > > simple_attr::get_buf if it hasn't been filled yet.
> > > >
> > > > Reported-by: [email protected]
> > > > Reported-by: Alexander Potapenko <[email protected]>
> > > > Fixes: acaefc25d21f ("[PATCH] libfs: add simple attribute files")
> > > > Cc: [email protected]
> > > > Signed-off-by: Eric Biggers <[email protected]>
> > > > ---
> > > > fs/libfs.c | 8 +++++---
> > > > 1 file changed, 5 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/fs/libfs.c b/fs/libfs.c
> > > > index c686bd9caac6..3759fbacf522 100644
> > > > --- a/fs/libfs.c
> > > > +++ b/fs/libfs.c
> > > > @@ -891,7 +891,7 @@ int simple_attr_open(struct inode *inode, struct file *file,
> > > > {
> > > > struct simple_attr *attr;
> > > >
> > > > - attr = kmalloc(sizeof(*attr), GFP_KERNEL);
> > > > + attr = kzalloc(sizeof(*attr), GFP_KERNEL);
> > > > if (!attr)
> > > > return -ENOMEM;
> > > >
> > > > @@ -931,9 +931,11 @@ ssize_t simple_attr_read(struct file *file, char __user *buf,
> > > > if (ret)
> > > > return ret;
> > > >
> > > > - if (*ppos) { /* continued read */
> > > > + if (*ppos && attr->get_buf[0]) {
> > > > + /* continued read */
> > > > size = strlen(attr->get_buf);
> > > > - } else { /* first read */
> > > > + } else {
> > > > + /* first read */
> > > > u64 val;
> > > > ret = attr->get(attr->data, &val);
> > > > if (ret)
> > > > --
> > > > 2.25.1
> > >
> > > Any comments on this? Al, seems this is something you should pick up?
> > >
> > > - Eric
> >
> > Ping.
> >
>
> Andrew, can you consider taking this patch? Al has been ignoring it, and this
> seems like a fairly important fix. This bug affects many (most?) debugfs files,
> and it affects years old kernels too not just recent ones.
As it affects debugfs files, I'll grab it now, thanks.
greg k-h