From: yangerkun
maillist inclusion
category: bugfix
issue: #I4NRS5
CVE: NA
Signed-off-by: Yu Changchun
---------------------------
Our stress testing with IO error can trigger follow OOB with a very low
probability.
[59898.282466] BUG: KASAN: slab-out-of-bounds in ext4_find_extent+0x2e4/0x480
...
[59898.287162] Call Trace:
[59898.287575] dump_stack+0x8b/0xb9
[59898.288070] print_address_description+0x73/0x280
[59898.289903] ext4_find_extent+0x2e4/0x480
[59898.290553] ext4_ext_map_blocks+0x125/0x1470
[59898.295481] ext4_map_blocks+0x5ee/0x940
[59898.315984] ext4_mpage_readpages+0x63c/0xdb0
[59898.320231] read_pages+0xe6/0x370
[59898.321589] __do_page_cache_readahead+0x233/0x2a0
[59898.321594] ondemand_readahead+0x157/0x450
[59898.321598] generic_file_read_iter+0xcb2/0x1550
[59898.328828] __vfs_read+0x233/0x360
[59898.328840] vfs_read+0xa5/0x190
[59898.330126] ksys_read+0xa5/0x150
[59898.331405] do_syscall_64+0x6d/0x1f0
[59898.331418] entry_SYSCALL_64_after_hwframe+0x44/0xa9
Digging deep and we found it's actually a xattr block which can happened
with follow steps:
1. extent update for file1 and will remove a leaf extent block(block A)
2. we need update the idx extent block too
3. block A has been allocated as a xattr block and will set verified
3. io error happened for this idx block and will the buffer has been
released late
4. extent find for file1 will read the idx block and see block A again
5. since the buffer of block A is already verified, we will use it
directly, which can lead the upper OOB
Same as __ext4_xattr_check_block, we can check magic even the buffer is
verified to fix the problem.
Signed-off-by: yangerkun
Reviewed-by: Zhang Yi
Signed-off-by: Chen Jun
Signed-off-by: Zheng Zengkai
Signed-off-by: Yu Changchun
---
fs/ext4/extents.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index a77e25ca6867..74b69d83c198 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -545,6 +545,14 @@ __read_extent_tree_block(const char *function, unsigned int line,
goto errout;
}
if (buffer_verified(bh)) {
+ if (unlikely(ext_block_hdr(bh)->eh_magic != EXT4_EXT_MAGIC)) {
+ err = -EFSCORRUPTED;
+ ext4_error_inode(inode, function, line, 0,
+ "invalid magic for verified extent block %llu",
+ (unsigned long long)bh->b_blocknr);
+ goto errout;
+ }
+
if (!(flags & EXT4_EX_FORCE_CACHE))
return bh;
} else {
--
2.25.1
