Messages in this thread | | | Date | Sun, 30 Jul 2017 22:16:41 +0200 | From | Dominik Brodowski <> | Subject | Re: lsipc(1) triggers general protection fault in sysvipc_shm_proc_show() on v4.13-rc2+ |
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Kees,
thanks for taking a look at this!
On Sun, Jul 30, 2017 at 10:47:21AM -0700, Kees Cook wrote: > On Sun, Jul 30, 2017 at 9:28 AM, Kees Cook <keescook@chromium.org> wrote: > > On Sun, Jul 30, 2017 at 3:10 AM, Dominik Brodowski > > <linux@dominikbrodowski.net> wrote: > >> Kees, Manfred, > >> > >> on Linus' most recent kernel (v4.13-rc2+, git head 0a07b238e5f48), lsipc(1) > >> works as expected in initramfs and before gnome starts up. Afterwards, > >> running lsipc as user(!) results in the following general protection fault > >> and a quite unusable system: > >> > >> [ 183.018415] general protection fault: 0000 [#1] PREEMPT SMP > >> [ 183.018486] Modules linked in: > >> [ 183.018521] CPU: 2 PID: 1964 Comm: lsipc Not tainted 4.13.0-rc2+ #2 > >> [ 183.018575] Hardware name: Dell Inc. XPS 13 9343/0TM99H, BIOS A11 12/08/2016 > >> [ 183.018636] task: ffff9f0651708000 task.stack: ffffa8d3837d0000 > >> [ 183.018692] RIP: 0010:shm_add_rss_swap.isra.1+0x13/0xa0 > >> [ 183.018738] RSP: 0018:ffffa8d3837d3d78 EFLAGS: 00010246 > >> [ 183.018785] RAX: 6b6b6b6b6b6b6b6b RBX: ffff9f065c29cc70 RCX: 0000000000000000 > >> [ 183.018845] RDX: ffffa8d3837d3de0 RSI: ffffa8d3837d3dd8 RDI: ffff9f065c29cd50 > >> [ 183.018905] RBP: ffffa8d3837d3d98 R08: 0000000000000000 R09: ffff9f065c29cc70 > >> [ 183.018965] R10: 0000000000000040 R11: 0000000000000000 R12: ffffffff8bc5b9a0 > >> [ 183.019026] R13: ffff9f063838a280 R14: ffff9f065c29cc70 R15: ffff9f068bcecaa0 > >> [ 183.019088] FS: 00007cec9dce2700(0000) GS:ffff9f069f500000(0000) knlGS:0000000000000000 > >> [ 183.019156] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > >> [ 183.019206] CR2: 00007ffe4e7a8ff8 CR3: 000000020b9ca000 CR4: 00000000003406e0 > >> [ 183.019265] Call Trace: > >> [ 183.019294] sysvipc_shm_proc_show+0x5e/0x150 > >> [ 183.019338] ? _raw_spin_lock+0x17/0x40 > >> [ 183.019376] ? sysvipc_find_ipc+0xbc/0xf0 > >> [ 183.019416] sysvipc_proc_show+0x1a/0x30 > >> [ 183.019456] seq_read+0x2e9/0x3f0 > >> [ 183.019492] proc_reg_read+0x42/0x70 > >> [ 183.019528] __vfs_read+0x18/0x40 > >> [ 183.019562] vfs_read+0x8e/0x110 > >> [ 183.019595] SyS_read+0x55/0xc0 > >> [ 183.019629] entry_SYSCALL_64_fastpath+0x18/0xa8 > >> [ 183.019671] RIP: 0033:0x7cec9d5fcb90 > >> [ 183.019703] RSP: 002b:00007ffe4e7a97d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 > >> [ 183.019769] RAX: ffffffffffffffda RBX: 000007e254b1a221 RCX: 00007cec9d5fcb90 > >> [ 183.019829] RDX: 0000000000000400 RSI: 000007e255712020 RDI: 0000000000000003 > >> [ 183.019890] RBP: 00007cec9d8ba588 R08: 0000000000000003 R09: 000000000000007c > >> [ 183.019950] R10: 0000000000000040 R11: 0000000000000246 R12: 00007cec9d8b9820 > >> [ 183.020010] R13: 0000000000000011 R14: 00007ffe4e7a95b0 R15: 00007ffe4e7a95b0 > >> [ 183.020071] Code: 7f 18 48 89 e5 e8 5e ff ff ff 85 c0 75 02 5d c3 0f ff 5d c3 0f 1f 40 00 0f 1f 44 00 00 55 48 89 e5 41 56 41 55 41 54 53 48 8b 07 <4c> 8b 60 08 48 8b 40 68 48 3d 80 13 47 8b 74 08 48 3d 00 15 45 > >> [ 183.020290] RIP: shm_add_rss_swap.isra.1+0x13/0xa0 RSP: ffffa8d3837d3d78 > >> [ 183.042734] ---[ end trace c5a8076d8f19909f ]--- > >> [ 183.042740] note: lsipc[1964] exited with preempt_count 1 > > > > Can you send your config? Also, are you able to do a bisect to find > > the specific commit that is triggering this? Are there any interesting > > dmesg lines before the general protection fault line? > > Ah, I have been able to reproduce this now. I'll see if I can track this down... > > [ 20.640404] BUG: unable to handle kernel NULL pointer dereference > at 0000000000000088
I've bisected it to between v4.13-rc1 and 96080f697786 so far, ~7 more kernels/reboots to go. That leaves no code changes to ipc/, but some randstruct changes ( I have set CONFIG_GCC_PLUGIN_RANDSTRUCT=y ) which touch some ipc-related code.
And since you asked: When I triggered the general protection fault, no NULL pointer message or other notable line was printed out in dmesg. When testing 96080f697786, I triggered a NULL pointer as well, but no general protection fault.
Best, Dominik
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