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mm: fix use-after-free in sys_remap_file_pages

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remap_file_pages calls mmap_region, which may merge the VMA with other
existing VMAs, and free "vma".  This can lead to a use-after-free bug.
Avoid the bug by remembering vm_flags before calling mmap_region, and
not trying to dereference vma later.

Signed-off-by: Rik van Riel <riel@redhat.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Kees Cook <keescook@chromium.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rik van Riel 2014-01-02 12:58:46 -08:00 committed by Linus Torvalds
parent 3b25df93c6
commit 4eb919825e
1 changed files with 5 additions and 3 deletions
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8
mm/fremap.c
View file

@ -208,9 +208,10 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
if (mapping_cap_account_dirty(mapping)) {
unsigned long addr;
struct file *file = get_file(vma->vm_file);
/* mmap_region may free vma; grab the info now */
vm_flags = vma->vm_flags;
addr = mmap_region(file, start, size,
vma->vm_flags, pgoff);
addr = mmap_region(file, start, size, vm_flags, pgoff);
fput(file);
if (IS_ERR_VALUE(addr)) {
err = addr;
@ -218,7 +219,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
BUG_ON(addr != start);
err = 0;
}
goto out;
goto out_freed;
}
mutex_lock(&mapping->i_mmap_mutex);
flush_dcache_mmap_lock(mapping);
@ -253,6 +254,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
out:
if (vma)
vm_flags = vma->vm_flags;
out_freed:
if (likely(!has_write_lock))
up_read(&mm->mmap_sem);
else