Re: [syzbot] general protection fault in vma_interval_tree_remove

[Liam Howlett <liam.howlett@oracle.com>]

* Andrew Morton <akpm@linux-foundation.org> [220514 16:50]:
> On Sat, 14 May 2022 13:18:26 -0700 syzbot <syzbot+ee1fdd8dcc770a3a169a@syzkaller.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@syzkaller.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
> >