linux-kernel - Bug introduced in 3b93f911d5

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 8 Aug 2014 00:11:39 +0100
From:	Anton Altaparmakov <aia21@....ac.uk>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Bug introduced in 3b93f911d5

Hi Al,

Was just looking at __generic_file_write_iter() and found a bug in the code that you added in 3b93f911d5.

Consider the case where generic_file_direct_write() returns a partial write, i.e. written > 0 && written < count.

Also consider that the following generic_perform_write() fails with an error, i.e. status < 0.

This code then does something very bogus:

		if (unlikely(status < 0) && !written) {
			err = status;
			goto out;
		}
		iocb->ki_pos = pos + status;
		...
		endbyte = pos + status - 1;

The if condition is false as written is > 0 yet status is negative thus iocb->ki_pos is set to pos + status where status is negative thus ki_pos is actually set to "pos - random value".

And similar for "endbyte" being set to "pos - random value - 1", etc.

Doesn't seem like that is what you intended?

Best regards,

	Anton
-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
University of Cambridge Information Services, Roger Needham Building
7 JJ Thomson Avenue, Cambridge, CB3 0RB, UK

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/