diff options
| author | Sahitya Tummala | 2019-05-10 22:00:33 -0400 |
|---|---|---|
| committer | Theodore Ts'o | 2019-05-10 22:00:33 -0400 |
| commit | 08fc98a4d6424af66eb3ac4e2cedd2fc927ed436 (patch) | |
| tree | 0868ad014fc042281419f981e93c5e40050d1cf7 | |
| parent | 57a0da28ced8707cb9f79f071a016b9d005caf5a (diff) | |
ext4: fix use-after-free in dx_release()
The buffer_head (frames[0].bh) and it's corresping page can be
potentially free'd once brelse() is done inside the for loop
but before the for loop exits in dx_release(). It can be free'd
in another context, when the page cache is flushed via
drop_caches_sysctl_handler(). This results into below data abort
when accessing info->indirect_levels in dx_release().
Unable to handle kernel paging request at virtual address ffffffc17ac3e01e
Call trace:
dx_release+0x70/0x90
ext4_htree_fill_tree+0x2d4/0x300
ext4_readdir+0x244/0x6f8
iterate_dir+0xbc/0x160
SyS_getdents64+0x94/0x174
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Cc: stable@kernel.org
| -rw-r--r-- | fs/ext4/namei.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index e917830eae84..ac7457fef9e6 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -872,12 +872,15 @@ static void dx_release(struct dx_frame *frames) { struct dx_root_info *info; int i; + unsigned int indirect_levels; if (frames[0].bh == NULL) return; info = &((struct dx_root *)frames[0].bh->b_data)->info; - for (i = 0; i <= info->indirect_levels; i++) { + /* save local copy, "info" may be freed after brelse() */ + indirect_levels = info->indirect_levels; + for (i = 0; i <= indirect_levels; i++) { if (frames[i].bh == NULL) break; brelse(frames[i].bh); |