Re: [syzbot] general protection fault in mod_memcg_page_state

From: Michal Hocko
Date: Thu Dec 30 2021 - 03:53:07 EST

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[Cc Shakeel]

On Wed 29-12-21 17:54:21, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: ea586a076e8a Add linux-next specific files for 20211224
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=16dc61edb00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=a9c4e3dde2c568fb
> dashboard link: https://syzkaller.appspot.com/bug?extid=864849a13d44b22de04d
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17371b99b00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14519ac3b00000
>
> The issue was bisected to:
>
> commit e4b8954074f6d0db01c8c97d338a67f9389c042f
> Author: Eric Dumazet <edumazet@xxxxxxxxxx>
> Date: Tue Dec 7 01:30:37 2021 +0000
>
> netlink: add net device refcount tracker to struct ethnl_req_info
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14f00ddbb00000
> final oops: https://syzkaller.appspot.com/x/report.txt?x=16f00ddbb00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=12f00ddbb00000

I am confused. The above log points to the following warning and
a consequent panic_on_warn
WARNING: CPU: 0 PID: 10 at lib/ref_tracker.c:38 ref_tracker_dir_exit.cold+0x163/0x1b4
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+864849a13d44b22de04d@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: e4b8954074f6 ("netlink: add net device refcount tracker to struct ethnl_req_info")
>
> general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
> CPU: 1 PID: 3677 Comm: syz-executor257 Not tainted 5.16.0-rc6-next-20211224-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:_compound_head include/linux/page-flags.h:263 [inline]
> RIP: 0010:page_memcg include/linux/memcontrol.h:452 [inline]
> RIP: 0010:mod_memcg_page_state.part.0.constprop.0+0x28/0x5b0 include/linux/memcontrol.h:957

This might have something to do with http://lkml.kernel.org/r/20211222052457.1960701-1-shakeelb@xxxxxxxxxx
which has added the accounting which is blowing up. The problem happens
when a memcg is retrieved from the allocated page. This should be NULL
as the reported commit doesn't really add any __GFP_ACCOUNT user AFAICS.
Anyway vm_area_alloc_pages can fail the allocation if the current
context has fatal signals pending. array->pages array is allocated with
__GFP_ZERO so the failed allocation should have kept the pages[0] NULL.
I haven't followed the page->memcg path to double check whether that
could lead to 0xdffffc0000000001 in the end.

I believe we need something like
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 9bf838817a47..d2e392cac909 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2627,7 +2627,8 @@ static void __vunmap(const void *addr, int deallocate_pages)
unsigned int page_order = vm_area_page_order(area);
int i;

- mod_memcg_page_state(area->pages[0], MEMCG_VMALLOC,
+ if (area->pages[0])
+ mod_memcg_page_state(area->pages[0], MEMCG_VMALLOC,
-area->nr_pages);

for (i = 0; i < area->nr_pages; i += 1U << page_order) {
@@ -2968,7 +2969,8 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
page_order, nr_small_pages, area->pages);

atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
- mod_memcg_page_state(area->pages[0], MEMCG_VMALLOC, area->nr_pages);
+ if (area->pages[0])
+ mod_memcg_page_state(area->pages[0], MEMCG_VMALLOC, area->nr_pages);

/*
* If not enough pages were obtained to accomplish an

Or to account each page separately so that we do not have to rely on
pages[0].

> Code: 00 90 41 56 41 55 41 54 41 89 f4 55 48 89 fd 53 4c 8d 6d 08 e8 49 dd c1 ff 4c 89 ea 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 11 05 00 00 4c 8b 75 08 31 ff 4c 89 f3 83 e3 01
> RSP: 0018:ffffc900028bf5c0 EFLAGS: 00010202
>
> RAX: dffffc0000000000 RBX: 0000000000000001 RCX: 0000000000000000
> RDX: 0000000000000001 RSI: ffffffff81b62737 RDI: 0000000000000000
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
> R10: ffffffff81b745c0 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000008 R14: ffff88807ee9b628 R15: ffff88807ee9b600
> FS: 00007f8d769be700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007ffe642c4960 CR3: 000000006fc65000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> mod_memcg_page_state mm/vmalloc.c:2971 [inline]
> __vmalloc_area_node mm/vmalloc.c:2971 [inline]
> __vmalloc_node_range+0x678/0xf80 mm/vmalloc.c:3106
> __vmalloc_node mm/vmalloc.c:3156 [inline]
> vmalloc+0x67/0x80 mm/vmalloc.c:3197
> bpf_prog_calc_tag+0xc9/0x6c0 kernel/bpf/core.c:279
> resolve_pseudo_ldimm64 kernel/bpf/verifier.c:11925 [inline]
> bpf_check+0x1c86/0xbac0 kernel/bpf/verifier.c:14279
> bpf_prog_load+0xf55/0x21f0 kernel/bpf/syscall.c:2344
> __sys_bpf+0x68a/0x5970 kernel/bpf/syscall.c:4634
> __do_sys_bpf kernel/bpf/syscall.c:4738 [inline]
> __se_sys_bpf kernel/bpf/syscall.c:4736 [inline]
> __x64_sys_bpf+0x75/0xb0 kernel/bpf/syscall.c:4736
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7f8d76a0cd09
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f8d769be2f8 EFLAGS: 00000246
> ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 00007f8d76a954a8 RCX: 00007f8d76a0cd09
> RDX: 0000000000000080 RSI: 0000000020000200 RDI: 0000000000000005
> RBP: 00007f8d76a954a0 R08: 0000000000000002 R09: 0000000000003032
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
> R13: 00007f8d769be300 R14: 00007f8d769be400 R15: 0000000000022000
> </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:_compound_head include/linux/page-flags.h:263 [inline]
> RIP: 0010:page_memcg include/linux/memcontrol.h:452 [inline]
> RIP: 0010:mod_memcg_page_state.part.0.constprop.0+0x28/0x5b0 include/linux/memcontrol.h:957
> Code: 00 90 41 56 41 55 41 54 41 89 f4 55 48 89 fd 53 4c 8d 6d 08 e8 49 dd c1 ff 4c 89 ea 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 11 05 00 00 4c 8b 75 08 31 ff 4c 89 f3 83 e3 01
> RSP: 0018:ffffc900028bf5c0 EFLAGS: 00010202
>
> RAX: dffffc0000000000 RBX: 0000000000000001 RCX: 0000000000000000
> RDX: 0000000000000001 RSI: ffffffff81b62737 RDI: 0000000000000000
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
> R10: ffffffff81b745c0 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000008 R14: ffff88807ee9b628 R15: ffff88807ee9b600
> FS: 00007f8d769be700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f8d76a76e84 CR3: 000000006fc65000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
> 0: 00 90 41 56 41 55 add %dl,0x55415641(%rax)
> 6: 41 54 push %r12
> 8: 41 89 f4 mov %esi,%r12d
> b: 55 push %rbp
> c: 48 89 fd mov %rdi,%rbp
> f: 53 push %rbx
> 10: 4c 8d 6d 08 lea 0x8(%rbp),%r13
> 14: e8 49 dd c1 ff callq 0xffc1dd62
> 19: 4c 89 ea mov %r13,%rdx
> 1c: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
> 23: fc ff df
> 26: 48 c1 ea 03 shr $0x3,%rdx
> * 2a: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
> 2e: 0f 85 11 05 00 00 jne 0x545
> 34: 4c 8b 75 08 mov 0x8(%rbp),%r14
> 38: 31 ff xor %edi,%edi
> 3a: 4c 89 f3 mov %r14,%rbx
> 3d: 83 e3 01 and $0x1,%ebx
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches

--
Michal Hocko
SUSE Labs

Next message: Uwe Kleine-König: "Re: [PATCH v3 00/23] counter: cleanups and device lifetime fixes"
Previous message: Yifeng Zhao: "[PATCH v7 4/4] arm64: dts: rockchip: add naneng combo phy nodes for rk3568"
In reply to: syzbot: "[syzbot] general protection fault in mod_memcg_page_state"
Next in thread: Shakeel Butt: "Re: [syzbot] general protection fault in mod_memcg_page_state"
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