linux-ext4 - [Bug 200933] Divide zero in __ext4_check_dir

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Message-ID: <bug-200933-13602-Z0CU2e0tu3@https.bugzilla.kernel.org/>
Date:   Fri, 31 Aug 2018 17:31:15 +0000
From:   bugzilla-daemon@...zilla.kernel.org
To:     linux-ext4@...nel.org
Subject: [Bug 200933] Divide zero in __ext4_check_dir_entry

https://bugzilla.kernel.org/show_bug.cgi?id=200933

--- Comment #4 from Theodore Tso (tytso@....edu) ---
Revised description:

ext4: avoid divide by zero fault when deleting corrupted inline directories

A specially crafted file system can trick empty_inline_dir() into
reading past the last valid entry in a inline directory, and then run
into the end of xattr marker. This will trigger a divide by zero
fault.  Fix this by using the size of the inline directory instead of
dir->i_size.

Also clean up error reporting in __ext4_check_dir_entry so that the
message is clearer and more understandable --- and avoids the division
by zero trap if the size passed in is zero.  (I'm not sure why we
coded it that way in the first place; printing offset % size is
actually more confusing and less useful.)

https://bugzilla.kernel.org/show_bug.cgi?id=200933

Signed-off-by: Theodore Ts'o <tytso@....edu>
Reported-by: Wen Xu <wen.xu@...ech.edu>
Cc: stable@...r.kernel.org

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