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Date: Mon, 27 Mar 2017 18:00:14 +0100
From: Mark Rutland <mark.rutland@....com>
To: linux-kernel@...r.kernel.org
Cc: Mark Rutland <mark.rutland@....com>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
"David S. Miller" <davem@...emloft.net>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
James Morris <jmorris@...ei.org>,
Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org
Subject: [PATCH] net: ipconfig: fix ic_close_devs() use-after-free
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@....com>
Cc: Alexey Kuznetsov <kuznet@....inr.ac.ru>
Cc: David S. Miller <davem@...emloft.net>
Cc: Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Cc: James Morris <jmorris@...ei.org>
Cc: Patrick McHardy <kaber@...sh.net>
Cc: netdev@...r.kernel.org
---
net/ipv4/ipconfig.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
index fd9f34b..dfb2ab2 100644
--- 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);
}
--
1.9.1
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