Messages in this thread Patch in this message | | | Date | Wed, 2 Sep 2009 16:02:01 +0200 | From | Ingo Molnar <> | Subject | [PATCH, v3] isdn: Fix stack corruption in isdnloop_init() |
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* Arjan van de Ven <arjan@infradead.org> wrote:
> > - char rev[10]; > > + char rev[strlen(revision)+1]; > > > > if ((p = strchr(revision, ':'))) { > > strcpy(rev, p + 1); > > now it;s a runtime variable sized array. > NotNice(tm)
ah, indeed - i thought GCC would figure out its constness but it doesnt. v3 should fix this:
--------------> From aa9aff8c2633cf24ad6465d8bf5aa93aa5d91f83 Mon Sep 17 00:00:00 2001 From: Ingo Molnar <mingo@elte.hu> Date: Tue, 26 May 2009 21:18:22 +0200 Subject: [PATCH] isdn: Fix stack corruption in isdnloop_init()
-tip testing found this stack corruption and bootup crash in the ISDN subsystem, reported by stackprotector:
[ 25.656688] calling isdn_init+0x0/0x2c2 @ 1 [ 25.660388] ISDN subsystem Rev: 1.1.2.3/1.1.2.3/1.1.2.2/1.1.2.3/1.1.2.2/1.1.2.2 [ 25.668179] initcall isdn_init+0x0/0x2c2 returned 0 after 6510 usecs [ 25.670005] calling isdn_bsdcomp_init+0x0/0x45 @ 1 [ 25.673336] PPP BSD Compression module registered [ 25.676674] initcall isdn_bsdcomp_init+0x0/0x45 returned 0 after 3255 usecs [ 25.680005] calling isdnloop_init+0x0/0x88 @ 1 [ 25.683337] isdnloop-ISDN-driver Rev 1.11.6.7 [ 25.686705] isdnloop: (loop0) virtual card added [ 25.690004] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: c1de2d8b [ 25.690006] [ 25.693338] Pid: 1, comm: swapper Not tainted 2.6.31-rc8-tip-01250-geed031c-dirty #9565 [ 25.696672] Call Trace: [ 25.700008] [<c190f517>] ? printk+0x1d/0x30 [ 25.703339] [<c190f45d>] panic+0x50/0xed [ 25.706677] [<c1059194>] __stack_chk_fail+0x1e/0x42 [ 25.710005] [<c1de2d8b>] ? isdnloop_init+0x83/0x88 [ 25.713338] [<c1de2d8b>] isdnloop_init+0x83/0x88 [ 25.716674] [<c1001056>] _stext+0x56/0x15a [ 25.720007] [<c1da8368>] kernel_init+0x8f/0xf1 [ 25.723338] [<c1da82d9>] ? kernel_init+0x0/0xf1 [ 25.726675] [<c1025c67>] kernel_thread_helper+0x7/0x58 [ 25.730005] Rebooting in 1 seconds..Press any key to enter the menu
The bug is that the temporary array:
char rev[10];
Is sized one byte too small to store strings based on the 'revision' string.
This is a truly ancient bug: it has been introduced in the v2.4.2.1 kernel, ~8.5 years ago, which extended the length of 'revision' by 1 byte.
Instead of using a fixed size temporary array, size it based on the 'revision' string.
Cc: <stable@kernel.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> --- drivers/isdn/isdnloop/isdnloop.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/isdn/isdnloop/isdnloop.c b/drivers/isdn/isdnloop/isdnloop.c index a335c85..ea07fdd 100644 --- a/drivers/isdn/isdnloop/isdnloop.c +++ b/drivers/isdn/isdnloop/isdnloop.c @@ -15,7 +15,7 @@ #include <linux/sched.h> #include "isdnloop.h" -static char *revision = "$Revision: 1.11.6.7 $"; +static char revision[] = "$Revision: 1.11.6.7 $"; static char *isdnloop_id = "loop0"; MODULE_DESCRIPTION("ISDN4Linux: Pseudo Driver that simulates an ISDN card"); @@ -1494,7 +1494,7 @@ static int __init isdnloop_init(void) { char *p; - char rev[10]; + char rev[sizeof(revision)]; if ((p = strchr(revision, ':'))) { strcpy(rev, p + 1);
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