Re: [syzbot] kernel panic: corrupted stack end in openat
From: Arnd Bergmann <arnd@arndb.de>
Date: 2021-03-16 16:29:35
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linux-mm, lkml
On Tue, Mar 16, 2021 at 5:13 PM Dmitry Vyukov [off-list ref] wrote:
On Tue, Mar 16, 2021 at 5:03 PM Arnd Bergmann [off-list ref] wrote:quoted
On Tue, Mar 16, 2021 at 4:51 PM Russell King - ARM Linux admin [off-list ref] wrote:quoted
On Tue, Mar 16, 2021 at 04:44:45PM +0100, Arnd Bergmann wrote:quoted
On Tue, Mar 16, 2021 at 11:17 AM Dmitry Vyukov [off-list ref] wrote:quoted
The compiler is gcc version 10.2.1 20210110 (Debian 10.2.1-6)Ok, building with Ubuntu 10.2.1-1ubuntu1 20201207 locally, that's the closest I have installed, and I think the Debian and Ubuntu versions are generally quite close in case of gcc since they are maintained by the same packagers.... which shouldn't be a problem - that's just over 1/4 of the stack space. Could it be the syzbot's gcc is doing something weird and inflating the stack frames?It's possible, I think that's really unlikely given that it's just Debian's gcc, which is as close to mainline as the version I was using. Uwe's DEBUG_STACKOVERFLOW patch from a while ago might help if this was the problem though: https://lore.kernel.org/linux-arm-kernel/20200108082913.29710-1-u.kleine-koenig@pengutronix.de/ (local) My best guess is something going wrong in the interrupt that triggered the preempt_schedule() which ended up calling task_stack_end_corrupted() in schedule_debug(), as you suggested earlier.FWIW I see slightly larger frames with the config: 073ab64 <ima_calc_field_array_hash_tfm>: 8073ab64: e1a0c00d mov ip, sp 8073ab68: e92ddff0 push {r4, r5, r6, r7, r8, r9, sl, fp, ip, lr, pc} 8073ab6c: e24cb004 sub fp, ip, #4 8073ab70: e24ddfa7 sub sp, sp, #668 ; 0x29c
Yes, this is the one that the compiler complained about when warning for stack over 600 bytes. It's not called in this call chain though.
page_alloc can also do reclaim, I had the impression that reclaim can be quite heavy-weight in all respects.
Yes, that is another possibility. What writable file systems or swap
do you normally have mounted that it could be writing to, and on
what storage device?
Arnd
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