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squashfs: fix length field overlap check in metadata reading 

This is a regression introduced by the "migrate from ll_rw_block usage
to BIO" patch.

Squashfs packs structures on byte boundaries, and due to that the length
field (of the metadata block) may not be fully in the current block.
The new code rewrote and introduced a faulty check for that edge case.

Fixes: 93e72b3c61 ("squashfs: migrate from ll_rw_block usage to BIO")
Reported-by: Bernd Amend <bernd.amend@gmail.com>
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Adrien Schildknecht <adrien+dev@schischi.me>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Daniel Rosenberg <drosen@google.com>
Link: http://lkml.kernel.org/r/20200717195536.16069-1-phillip@squashfs.org.uk
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
zero-sugar-mainline-defconfig
Phillip Lougher 2020-07-23 21:15:40 -07:00 committed by Linus Torvalds
parent e57942c563
commit 2910c59fd0
1 changed files with 1 additions and 1 deletions
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2
fs/squashfs/block.c
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@ -175,7 +175,7 @@ int squashfs_read_data(struct super_block *sb, u64 index, int length,
/* Extract the length of the metadata block */
data = page_address(bvec->bv_page) + bvec->bv_offset;
length = data[offset];
if (offset <= bvec->bv_len - 1) {
if (offset < bvec->bv_len - 1) {
length |= data[offset + 1] << 8;
} else {
if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {