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| author | Chandan Rajendra <chandan@linux.vnet.ibm.com> | 2017-12-11 15:00:57 -0500 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2017-12-11 15:00:57 -0500 |
| commit | 9d5afec6b8bd46d6ed821aa1579634437f58ef1f (patch) | |
| tree | fa959ddb7e55d7e89fe173eb4b58bf6fd090daa6 /fs | |
| parent | 996fc4477a0ea28226b30d175f053fb6f9a4fa36 (diff) | |
ext4: fix crash when a directory's i_size is too small
On a ppc64 machine, when mounting a fuzzed ext2 image (generated by
fsfuzzer) the following call trace is seen,
VFS: brelse: Trying to free free buffer
WARNING: CPU: 1 PID: 6913 at /root/repos/linux/fs/buffer.c:1165 .__brelse.part.6+0x24/0x40
.__brelse.part.6+0x20/0x40 (unreliable)
.ext4_find_entry+0x384/0x4f0
.ext4_lookup+0x84/0x250
.lookup_slow+0xdc/0x230
.walk_component+0x268/0x400
.path_lookupat+0xec/0x2d0
.filename_lookup+0x9c/0x1d0
.vfs_statx+0x98/0x140
.SyS_newfstatat+0x48/0x80
system_call+0x58/0x6c
This happens because the directory that ext4_find_entry() looks up has
inode->i_size that is less than the block size of the filesystem. This
causes 'nblocks' to have a value of zero. ext4_bread_batch() ends up not
reading any of the directory file's blocks. This renders the entries in
bh_use[] array to continue to have garbage data. buffer_uptodate() on
bh_use[0] can then return a zero value upon which brelse() function is
invoked.
This commit fixes the bug by returning -ENOENT when the directory file
has no associated blocks.
Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/ext4/namei.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 798b3ac680db..e750d68fbcb5 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -1399,6 +1399,10 @@ static struct buffer_head * ext4_find_entry (struct inode *dir, "falling back\n")); } nblocks = dir->i_size >> EXT4_BLOCK_SIZE_BITS(sb); + if (!nblocks) { + ret = NULL; + goto cleanup_and_exit; + } start = EXT4_I(dir)->i_dir_start_lookup; if (start >= nblocks) start = 0; |