| [PATCH] proc: check vma->vm_file before dereferencing [message #48349] |
Mon, 15 October 2012 15:30  |
Stanislav Kinsbursky
Messages: 683
Registered: October 2011
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Senior Member |
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It can be equal to NULL.
Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
---
fs/proc/base.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 144a967..74fc562 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1770,8 +1770,9 @@ static struct dentry *proc_map_files_lookup(struct inode *dir,
if (!vma)
goto out_no_vma;
- result = proc_map_files_instantiate(dir, dentry, task,
- (void *)(unsigned long)vma->vm_file->f_mode);
+ if (vma->vm_file)
+ result = proc_map_files_instantiate(dir, dentry, task,
+ (void *)(unsigned long)vma->vm_file->f_mode);
out_no_vma:
up_read(&mm->mmap_sem);
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| Re: [PATCH] proc: check vma->vm_file before dereferencing [message #48369 is a reply to message #48349] |
Mon, 15 October 2012 22:04  |
akpm
Messages: 224
Registered: March 2007
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Senior Member |
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On Tue, 16 Oct 2012 01:52:30 +0400
Cyrill Gorcunov <gorcunov@openvz.org> wrote:
> On Mon, Oct 15, 2012 at 02:40:48PM -0700, Andrew Morton wrote:
> > On Mon, 15 Oct 2012 19:30:03 +0400
> > Stanislav Kinsbursky <skinsbursky@parallels.com> wrote:
> >
> > > It can be equal to NULL.
> > >
> >
> > Please write better changelogs, so people do not have to ask questions
> > such as:
> >
> > - Under what conditions does this bug trigger?
> >
> > - In which kernel version(s)?
> >
> > - Is it a post-3.6 regression?
>
> Andrew, would the following changelog be enough?
>
> The commit 7b540d0646ce122f0ba4520412be91e530719742 switched
> proc_map_files_readdir to use @f_mode directly instead of grabbing
> @file reference, but same time the test for @vm_file presence was
> lost leading to nil dereference. The patch brings the test back.
>
> The all proc_map_files feature is CONFIG_CHECKPOINT_RESTORE wrapped
> (which is set to 'n' by default) so the bug doesn't affect regular
> kernels.
>
> The regression is 3.7-rc1 only as far as I can tell.
Ah, I see, great, thanks.
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