path: root/fs/ext4/namei.c
diff options
authorChandan Rajendra <chandan@linux.vnet.ibm.com>2017-12-11 15:00:57 -0500
committerTheodore Ts'o <tytso@mit.edu>2017-12-11 15:00:57 -0500
commit9d5afec6b8bd46d6ed821aa1579634437f58ef1f (patch)
treefa959ddb7e55d7e89fe173eb4b58bf6fd090daa6 /fs/ext4/namei.c
parent996fc4477a0ea28226b30d175f053fb6f9a4fa36 (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/ext4/namei.c')
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;