This is a note to let you know that I've just added the patch titled

net: ipconfig: fix ic_close_devs() use-after-free

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: net-ipconfig-fix-ic_close_devs-use-after-free.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Dec 21 09:02:40 CET 2017

From: Mark Rutland mark.rutland@arm.com Date: Mon, 27 Mar 2017 18:00:14 +0100 Subject: net: ipconfig: fix ic_close_devs() use-after-free

From: Mark Rutland mark.rutland@arm.com

[ Upstream commit ffefb6f4d6ad699a2b5484241bc46745a53235d0 ]

Our chosen ic_dev may be anywhere in our list of ic_devs, and we may free it before attempting to close others. When we compare d->dev and ic_dev->dev, we're potentially dereferencing memory returned to the allocator. This causes KASAN to scream for each subsequent ic_dev we check.

As there's a 1-1 mapping between ic_devs and netdevs, we can instead compare d and ic_dev directly, which implicitly handles the !ic_dev case, and avoids the use-after-free. The ic_dev pointer may be stale, but we will not dereference it.

Original splat:

[ 6.487446] ================================================================== [ 6.494693] BUG: KASAN: use-after-free in ic_close_devs+0xc4/0x154 at addr ffff800367efa708 [ 6.503013] Read of size 8 by task swapper/0/1 [ 6.507452] CPU: 5 PID: 1 Comm: swapper/0 Not tainted 4.11.0-rc3-00002-gda42158 #8 [ 6.514993] Hardware name: AppliedMicro Mustang/Mustang, BIOS 3.05.05-beta_rc Jan 27 2016 [ 6.523138] Call trace: [ 6.525590] [<ffff200008094778>] dump_backtrace+0x0/0x570 [ 6.530976] [<ffff200008094d08>] show_stack+0x20/0x30 [ 6.536017] [<ffff200008bee928>] dump_stack+0x120/0x188 [ 6.541231] [<ffff20000856d5e4>] kasan_object_err+0x24/0xa0 [ 6.546790] [<ffff20000856d924>] kasan_report_error+0x244/0x738 [ 6.552695] [<ffff20000856dfec>] __asan_report_load8_noabort+0x54/0x80 [ 6.559204] [<ffff20000aae86ac>] ic_close_devs+0xc4/0x154 [ 6.564590] [<ffff20000aaedbac>] ip_auto_config+0x2ed4/0x2f1c [ 6.570321] [<ffff200008084b04>] do_one_initcall+0xcc/0x370 [ 6.575882] [<ffff20000aa31de8>] kernel_init_freeable+0x5f8/0x6c4 [ 6.581959] [<ffff20000a16df00>] kernel_init+0x18/0x190 [ 6.587171] [<ffff200008084710>] ret_from_fork+0x10/0x40 [ 6.592468] Object at ffff800367efa700, in cache kmalloc-128 size: 128 [ 6.598969] Allocated: [ 6.601324] PID = 1 [ 6.603427] save_stack_trace_tsk+0x0/0x418 [ 6.607603] save_stack_trace+0x20/0x30 [ 6.611430] kasan_kmalloc+0xd8/0x188 [ 6.615087] ip_auto_config+0x8c4/0x2f1c [ 6.619002] do_one_initcall+0xcc/0x370 [ 6.622832] kernel_init_freeable+0x5f8/0x6c4 [ 6.627178] kernel_init+0x18/0x190 [ 6.630660] ret_from_fork+0x10/0x40 [ 6.634223] Freed: [ 6.636233] PID = 1 [ 6.638334] save_stack_trace_tsk+0x0/0x418 [ 6.642510] save_stack_trace+0x20/0x30 [ 6.646337] kasan_slab_free+0x88/0x178 [ 6.650167] kfree+0xb8/0x478 [ 6.653131] ic_close_devs+0x130/0x154 [ 6.656875] ip_auto_config+0x2ed4/0x2f1c [ 6.660875] do_one_initcall+0xcc/0x370 [ 6.664705] kernel_init_freeable+0x5f8/0x6c4 [ 6.669051] kernel_init+0x18/0x190 [ 6.672534] ret_from_fork+0x10/0x40 [ 6.676098] Memory state around the buggy address: [ 6.680880] ffff800367efa600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 6.688078] ffff800367efa680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 6.695276] >ffff800367efa700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 6.702469] ^ [ 6.705952] ffff800367efa780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 6.713149] ffff800367efa800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 6.720343] ================================================================== [ 6.727536] Disabling lock debugging due to kernel taint

Signed-off-by: Mark Rutland mark.rutland@arm.com Cc: Alexey Kuznetsov kuznet@ms2.inr.ac.ru Cc: David S. Miller davem@davemloft.net Cc: Hideaki YOSHIFUJI yoshfuji@linux-ipv6.org Cc: James Morris jmorris@namei.org Cc: Patrick McHardy kaber@trash.net Cc: netdev@vger.kernel.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/ipconfig.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/ipconfig.c +++ b/net/ipv4/ipconfig.c @@ -306,7 +306,7 @@ static void __init ic_close_devs(void) while ((d = next)) { next = d->next; dev = d->dev; - if ((!ic_dev || dev != ic_dev->dev) && !netdev_uses_dsa(dev)) { + if (d != ic_dev && !netdev_uses_dsa(dev)) { pr_debug("IP-Config: Downing %s\n", dev->name); dev_change_flags(dev, d->flags); }

Patches currently in stable-queue which might be from mark.rutland@arm.com are

queue-4.9/net-ipconfig-fix-ic_close_devs-use-after-free.patch