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authorRik van Riel <riel@redhat.com>2014-01-02 20:58:46 (GMT)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-09 20:24:24 (GMT)
commitabdd4b8ac01323900fcda70f6d9ee94b873d66e3 (patch)
tree6d246224f1abe56bd72862db4611b638625ccbcc /mm/fremap.c
parent398bbc5710f23c0db6ebd4dd30bb331086bd16e7 (diff)
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mm: fix use-after-free in sys_remap_file_pages
commit 4eb919825e6c3c7fb3630d5621f6d11e98a18b3a upstream. 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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm/fremap.c')
-rw-r--r--mm/fremap.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/mm/fremap.c b/mm/fremap.c
index 87da359..1fb6bfe 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -203,9 +203,10 @@ get_write_lock:
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;
@@ -213,7 +214,7 @@ get_write_lock:
BUG_ON(addr != start);
err = 0;
}
- goto out;
+ goto out_freed;
}
mutex_lock(&mapping->i_mmap_mutex);
flush_dcache_mmap_lock(mapping);
@@ -248,6 +249,7 @@ get_write_lock:
out:
if (vma)
vm_flags = vma->vm_flags;
+out_freed:
if (likely(!has_write_lock))
up_read(&mm->mmap_sem);
else