Re: GPF in shm_lock ipc

[Vlastimil Babka]

On 10/12/2015 11:55 AM, Dmitry Vyukov wrote:
> Hello,
>
> The following program crashes kernel:
>
> // autogenerated by syzkaller (http://github.com/google/syzkaller)
> #include <syscall.h>
> #include <string.h>
> #include <stdint.h>
>
> int main()
> {
>          long r0 = syscall(SYS_shmget, 0x0ul, 0x2ul, 0x8ul);
>          long r1 = syscall(SYS_shmat, r0, 0x20000000ul, 0x0ul);
>          long r2 = syscall(SYS_mremap, 0x20000000ul, 0x1000ul,
> 0x3000ul, 0x3ul, 0x207f9000ul);
>          long r19 = syscall(SYS_shmctl, r0, 0x0ul, 0);
>          long r20 = syscall(SYS_remap_file_pages, 0x207f9000ul,
> 0x3000ul, 0x0ul, 0x7ul, 0x0ul);
>          return 0;
> }
>
> On commit dd36d7393d6310b0c1adefb22fba79c3cf8a577c
> (git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git)
>
> ------------[ cut here ]------------
> WARNING: CPU: 2 PID: 2636 at ipc/shm.c:162 shm_open+0x74/0x80()
> Modules linked in:
> CPU: 2 PID: 2636 Comm: a.out Not tainted 4.3.0-rc3+ #37
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>   ffffffff81bcb43c ffff88081bf0bd70 ffffffff812fe8d6 0000000000000000
>   ffff88081bf0bda8 ffffffff81051ff1 ffffffffffffffea ffff88081b896ca8
>   ffff880819b81620 ffff8800bbaa6d00 ffff880819b81600 ffff88081bf0bdb8
> Call Trace:
>   [<     inline     >] __dump_stack lib/dump_stack.c:15
>   [<ffffffff812fe8d6>] dump_stack+0x44/0x5e lib/dump_stack.c:50
>   [<ffffffff81051ff1>] warn_slowpath_common+0x81/0xc0 kernel/panic.c:447
>   [<ffffffff810520e5>] warn_slowpath_null+0x15/0x20 kernel/panic.c:480
>   [<     inline     >] shm_lock ipc/shm.c:162
>   [<ffffffff81295c64>] shm_open+0x74/0x80 ipc/shm.c:196
>   [<ffffffff81295cbe>] shm_mmap+0x4e/0x80 ipc/shm.c:399 (discriminator 2)
>   [<ffffffff81142d14>] mmap_region+0x3c4/0x5e0 mm/mmap.c:1627
>   [<ffffffff81143227>] do_mmap+0x2f7/0x3d0 mm/mmap.c:1402
>   [<     inline     >] do_mmap_pgoff include/linux/mm.h:1930
>   [<     inline     >] SYSC_remap_file_pages mm/mmap.c:2694

Hmm what kind of stack unwinder catches inlines? Some external patch, 
based on debuginfo?

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