proc: check vma->vm_file before dereferencing
Commit 7b540d0646
("proc_map_files_readdir(): don't bother with
grabbing files") 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.
[gorcunov@openvz.org: provided changelog]
Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -1877,8 +1877,9 @@ static struct dentry *proc_map_files_lookup(struct inode *dir,
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if (!vma)
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if (!vma)
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goto out_no_vma;
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goto out_no_vma;
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result = proc_map_files_instantiate(dir, dentry, task,
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if (vma->vm_file)
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(void *)(unsigned long)vma->vm_file->f_mode);
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result = proc_map_files_instantiate(dir, dentry, task,
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(void *)(unsigned long)vma->vm_file->f_mode);
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out_no_vma:
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out_no_vma:
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up_read(&mm->mmap_sem);
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up_read(&mm->mmap_sem);
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