Lars, On 08.11.2016 14:43, Lars Ellenberg wrote: > From 3a5859e696178e31a25e65de58c461046fc52beb Mon Sep 17 00:00:00 2001 > From: Richard Weinberger <richard@xxxxxx> > Date: Tue, 8 Nov 2016 11:43:09 +0100 > Subject: [PATCH] drbd: Fix kernel_sendmsg() usage - potential NULL deref > drbd: Fix kernel_sendmsg() usage - potential NULL deref > > Don't pass a size larger than iov_len to kernel_sendmsg(). > Otherwise it will cause a NULL pointer deref when kernel_sendmsg() > returns with rv < size. > > DRBD as external module has been around in the kernel 2.4 days already. > We used to be compatible to 2.4 and very early 2.6 kernels, > we used to use > rv = sock_sendmsg(sock, &msg, iov.iov_len); > then later changed to > rv = kernel_sendmsg(sock, &msg, &iov, 1, size); > when we should have used > rv = kernel_sendmsg(sock, &msg, &iov, 1, iov.iov_len); > > tcp_sendmsg() used to totally ignore the size parameter. > 57be5bd ip: convert tcp_sendmsg() to iov_iter primitives > changes that, and exposes our long standing error. > > Even with this error exposed, to trigger the bug, we would need to have > an environment (config or otherwise) causing us to not use sendpage() > for larger transfers, a flaky connection, and have it fail "just at the > right time". Apparently that was unlikely enough for most, so this went > unnoticed for years. > > Still, it is known to trigger at least some of these, > and suspected for the others: > [0] http://lists.linbit.com/pipermail/drbd-user/2016-July/023112.html > [1] http://lists.linbit.com/pipermail/drbd-dev/2016-March/003362.html > [2] https://forums.grsecurity.net/viewtopic.php?f=3&t=4546 > [3] https://ubuntuforums.org/showthread.php?t=2336150 > [4] http://e2.howsolveproblem.com/i/1175162/ > > This should go into 4.9, > and into all stable branches since and including v4.0, > which is the first to contain the exposing change. > > It is correct for all stable branches older than that as well > (which contain the DRBD driver; which is 2.6.33 and up). > > It requires a small "conflict" resolution for v4.4 and earlier, with v4.5 > we dropped the comment block immediately preceding the kernel_sendmsg(). > > Cc: stable@xxxxxxxxxxxxxxx > Cc: viro@xxxxxxxxxxxxxxxxxx > Cc: christoph.lechleitner@xxxxxxx > Cc: wolfgang.glas@xxxxxxx > Reported-by: Christoph Lechleitner <christoph.lechleitner@xxxxxxx> > Tested-by: Christoph Lechleitner <christoph.lechleitner@xxxxxxx> > Signed-off-by: Richard Weinberger <richard@xxxxxx> > Signed-off-by: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx> Changing my patch is perfectly fine, but please clearly state it. I.e. by adding something like that before your S-o-b. [Lars: Massaged patch to match my personal taste...] Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html