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Message-ID: <20220516175958.cswumupmeddptzdb@revolver>
Date: Mon, 16 May 2022 18:00:06 +0000
From: Liam Howlett <liam.howlett@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
CC: syzbot <syzbot+ee1fdd8dcc770a3a169a@...kaller.appspotmail.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"syzkaller-bugs@...glegroups.com" <syzkaller-bugs@...glegroups.com>,
Michel Lespinasse <michel@...pinasse.org>
Subject: Re: [syzbot] general protection fault in vma_interval_tree_remove
* Andrew Morton <akpm@...ux-foundation.org> [220514 16:50]:
> On Sat, 14 May 2022 13:18:26 -0700 syzbot <syzbot+ee1fdd8dcc770a3a169a@...kaller.appspotmail.com> wrote:
>
> > syzbot has found a reproducer for the following issue on:
> >
> > HEAD commit: 1e1b28b936ae Add linux-next specific files for 20220513
> > git tree: linux-next
> > console+strace: https://syzkaller.appspot.com/x/log.txt?x=11da21b9f00000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=e4eb3c0c4b289571
> > dashboard link: https://syzkaller.appspot.com/bug?extid=ee1fdd8dcc770a3a169a
> > 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=142757f1f00000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17cf0966f00000
>
> Thanks.
>
> So it was there on April 28 and it's there now. Liam, do you think
> anything in the mapletree changes could have perturbed the interval
> tree handling?
It is certainly possible, these two trees are intertwined so much. One
area that sticks out as a possibility is vma_expand(). I created a
vma_expand() function to handle growing a vma and potentially removing
the next vma. I do some interval tree modifications in there.
I'll add it to my list of items to look at.
>
>
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+ee1fdd8dcc770a3a169a@...kaller.appspotmail.com
> >
> > general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
> > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> > CPU: 1 PID: 3612 Comm: syz-executor255 Not tainted 5.18.0-rc6-next-20220513-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > RIP: 0010:____rb_erase_color lib/rbtree.c:354 [inline]
> > RIP: 0010:__rb_erase_color+0x159/0xdb0 lib/rbtree.c:413
> > Code: 89 ed 48 89 c5 e9 f5 fe ff ff 4c 8d 45 10 4c 89 c0 48 c1 e8 03 80 3c 18 00 0f 85 3a 08 00 00 4c 8b 65 10 4c 89 e0 48 c1 e8 03 <80> 3c 18 00 0f 85 6a 08 00 00 49 8b 04 24 49 8d 7c 24 08 48 89 f9
> > RSP: 0018:ffffc90002e877a8 EFLAGS: 00010246
> > RAX: 0000000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
> > RDX: ffffed100e8d3aed RSI: ffff88807469d768 RDI: ffff8880202132b0
> > RBP: ffff8880202132b0 R08: ffff8880202132c0 R09: ffff88807469d75f
> > R10: ffffffff81b02518 R11: 0000000000000001 R12: 0000000000000000
> > R13: 0000000000000000 R14: ffff88807469d768 R15: ffffffff81b01300
> > FS: 0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007ffe92002ff8 CR3: 00000000764a0000 CR4: 00000000003506e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> > <TASK>
> > rb_erase_augmented include/linux/rbtree_augmented.h:305 [inline]
> > rb_erase_augmented_cached include/linux/rbtree_augmented.h:314 [inline]
> > vma_interval_tree_remove+0x694/0xed0 mm/interval_tree.c:23
> > __remove_shared_vm_struct mm/mmap.c:160 [inline]
> > unlink_file_vma+0xbd/0x110 mm/mmap.c:175
> > free_pgtables+0x255/0x420 mm/memory.c:440
> > exit_mmap+0x1ff/0x740 mm/mmap.c:3219
> > __mmput+0x128/0x4c0 kernel/fork.c:1180
> > mmput+0x5c/0x70 kernel/fork.c:1201
> > exit_mm kernel/exit.c:510 [inline]
> > do_exit+0xa18/0x2a00 kernel/exit.c:782
> > do_group_exit+0xd2/0x2f0 kernel/exit.c:925
> > get_signal+0x2542/0x2600 kernel/signal.c:2857
> > arch_do_signal_or_restart+0x82/0x20f0 arch/x86/kernel/signal.c:869
> > exit_to_user_mode_loop kernel/entry/common.c:166 [inline]
> > exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:201
> > irqentry_exit_to_user_mode+0x5/0x30 kernel/entry/common.c:307
> > exc_page_fault+0xc6/0x180 arch/x86/mm/fault.c:1543
> > asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:570
> > RIP: 0033:0x7f1771dc98cf
> > Code: Unable to access opcode bytes at RIP 0x7f1771dc98a5.
> > RSP: 002b:00007ffe920035a0 EFLAGS: 00010206
> > RAX: 0000000000000001 RBX: 00007f1771e78138 RCX: 0000000000000001
> > RDX: 0000000000000001 RSI: 00007f1771e78138 RDI: 000000000000000b
> > RBP: 000000000000000b R08: 0000000000000005 R09: 0000000000000000
> > R10: 0000000000008011 R11: 0000000000000206 R12: 0000000000000000
> > R13: 0000000000000001 R14: 00000000000c3ec0 R15: 0000000000000001
> > </TASK>
> > Modules linked in:
> > ---[ end trace 0000000000000000 ]---
> > RIP: 0010:____rb_erase_color lib/rbtree.c:354 [inline]
> > RIP: 0010:__rb_erase_color+0x159/0xdb0 lib/rbtree.c:413
> > Code: 89 ed 48 89 c5 e9 f5 fe ff ff 4c 8d 45 10 4c 89 c0 48 c1 e8 03 80 3c 18 00 0f 85 3a 08 00 00 4c 8b 65 10 4c 89 e0 48 c1 e8 03 <80> 3c 18 00 0f 85 6a 08 00 00 49 8b 04 24 49 8d 7c 24 08 48 89 f9
> > RSP: 0018:ffffc90002e877a8 EFLAGS: 00010246
> > RAX: 0000000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
> > RDX: ffffed100e8d3aed RSI: ffff88807469d768 RDI: ffff8880202132b0
> > RBP: ffff8880202132b0 R08: ffff8880202132c0 R09: ffff88807469d75f
> > R10: ffffffff81b02518 R11: 0000000000000001 R12: 0000000000000000
> > R13: 0000000000000000 R14: ffff88807469d768 R15: ffffffff81b01300
> > FS: 0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00000000000c3ec8 CR3: 0000000023516000 CR4: 00000000003506f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > ----------------
> > Code disassembly (best guess):
> > 0: 89 ed mov %ebp,%ebp
> > 2: 48 89 c5 mov %rax,%rbp
> > 5: e9 f5 fe ff ff jmpq 0xfffffeff
> > a: 4c 8d 45 10 lea 0x10(%rbp),%r8
> > e: 4c 89 c0 mov %r8,%rax
> > 11: 48 c1 e8 03 shr $0x3,%rax
> > 15: 80 3c 18 00 cmpb $0x0,(%rax,%rbx,1)
> > 19: 0f 85 3a 08 00 00 jne 0x859
> > 1f: 4c 8b 65 10 mov 0x10(%rbp),%r12
> > 23: 4c 89 e0 mov %r12,%rax
> > 26: 48 c1 e8 03 shr $0x3,%rax
> > * 2a: 80 3c 18 00 cmpb $0x0,(%rax,%rbx,1) <-- trapping instruction
> > 2e: 0f 85 6a 08 00 00 jne 0x89e
> > 34: 49 8b 04 24 mov (%r12),%rax
> > 38: 49 8d 7c 24 08 lea 0x8(%r12),%rdi
> > 3d: 48 89 f9 mov %rdi,%rcx
> >
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