squashfs: add more sanity checks in xattr id lookup
Sysbot has reported a warning where a kmalloc() attempt exceeds the maximum limit. This has been identified as corruption of the xattr_ids count when reading the xattr id lookup table. This patch adds a number of additional sanity checks to detect this corruption and others. 1. It checks for a corrupted xattr index read from the inode. This could be because the metadata block is uncompressed, or because the "compression" bit has been corrupted (turning a compressed block into an uncompressed block). This would cause an out of bounds read. 2. It checks against corruption of the xattr_ids count. This can either lead to the above kmalloc failure, or a smaller than expected table to be read. 3. It checks the contents of the index table for corruption. [phillip@squashfs.org.uk: fix checkpatch issue] Link: https://lkml.kernel.org/r/270245655.754655.1612770082682@webmail.123-reg.co.uk Link: https://lkml.kernel.org/r/20210204130249.4495-5-phillip@squashfs.org.ukSigned-off-by: Phillip Lougher <phillip@squashfs.org.uk> Reported-by: syzbot+2ccea6339d368360800d@syzkaller.appspotmail.com Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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