Re: BUG: Bad page state (5)

[Eric Biggers]

On Wed, Feb 13, 2019 at 12:23:31PM -0800, Andrew Morton wrote:
> On Wed, 13 Feb 2019 09:56:04 -0800 syzbot <syzbot+2cd2887ea471ed6e6995@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> 
> > Hello,
> > 
> > syzbot found the following crash on:
> > 
> > HEAD commit:    c4f3ef3eb53f Add linux-next specific files for 20190213
> > git tree:       linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1130a124c00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=9ec67976eb2df882
> > dashboard link: https://syzkaller.appspot.com/bug?extid=2cd2887ea471ed6e6995
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14ecdaa8c00000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12ebe178c00000
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+2cd2887ea471ed6e6995@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> It looks like a a memfd page was freed with a non-NULL ->mapping.
> 
> Joel touched the memfd code with "mm/memfd: add an F_SEAL_FUTURE_WRITE
> seal to memfd" but it would be surprising if syzbot tickled that code?
> 
> 
> > BUG: Bad page state in process udevd  pfn:472f0
> > name:"memfd:"
> > page:ffffea00011cbc00 count:0 mapcount:0 mapping:ffff88800df2ad40 index:0xf
> > shmem_aops
> > flags: 0x1fffc000008000c(uptodate|dirty|swapbacked)
> > raw: 01fffc000008000c ffffea0000ac4f08 ffff8880a85af890 ffff88800df2ad40
> > raw: 000000000000000f 0000000000000000 00000000ffffffff 0000000000000000
> > page dumped because: non-NULL mapping
> > Modules linked in:
> > CPU: 1 PID: 7586 Comm: udevd Not tainted 5.0.0-rc6-next-20190213 #34
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> > Google 01/01/2011
> > Call Trace:
> >   __dump_stack lib/dump_stack.c:77 [inline]
> >   dump_stack+0x172/0x1f0 lib/dump_stack.c:113
> >   bad_page.cold+0xda/0xff mm/page_alloc.c:586
> >   free_pages_check_bad+0x142/0x1a0 mm/page_alloc.c:1014
> >   free_pages_check mm/page_alloc.c:1023 [inline]
> >   free_pages_prepare mm/page_alloc.c:1113 [inline]
> >   free_pcp_prepare mm/page_alloc.c:1138 [inline]
> >   free_unref_page_prepare mm/page_alloc.c:2991 [inline]
> >   free_unref_page_list+0x31d/0xc40 mm/page_alloc.c:3060
> > name:"memfd:"
> >   release_pages+0x60d/0x1940 mm/swap.c:791
> >   pagevec_lru_move_fn+0x218/0x2a0 mm/swap.c:213
> >   __pagevec_lru_add mm/swap.c:917 [inline]
> >   lru_add_drain_cpu+0x2f7/0x520 mm/swap.c:581
> >   lru_add_drain+0x20/0x60 mm/swap.c:652
> >   exit_mmap+0x290/0x530 mm/mmap.c:3134
> >   __mmput kernel/fork.c:1047 [inline]
> >   mmput+0x15f/0x4c0 kernel/fork.c:1068
> >   exec_mmap fs/exec.c:1046 [inline]
> >   flush_old_exec+0x8d9/0x1c20 fs/exec.c:1279
> >   load_elf_binary+0x9bc/0x53f0 fs/binfmt_elf.c:864
> >   search_binary_handler fs/exec.c:1656 [inline]
> >   search_binary_handler+0x17f/0x570 fs/exec.c:1634
> >   exec_binprm fs/exec.c:1698 [inline]
> >   __do_execve_file.isra.0+0x1394/0x23f0 fs/exec.c:1818
> >   do_execveat_common fs/exec.c:1865 [inline]
> >   do_execve fs/exec.c:1882 [inline]
> >   __do_sys_execve fs/exec.c:1958 [inline]
> >   __se_sys_execve fs/exec.c:1953 [inline]
> >   __x64_sys_execve+0x8f/0xc0 fs/exec.c:1953
> >   do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
> >   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > RIP: 0033:0x7fc7001ba207
> > Code: Bad RIP value.
> > RSP: 002b:00007ffe06aa13b8 EFLAGS: 00000206 ORIG_RAX: 000000000000003b
> > RAX: ffffffffffffffda RBX: 00000000ffffffff RCX: 00007fc7001ba207
> > RDX: 0000000001fd5fd0 RSI: 00007ffe06aa14b0 RDI: 00007ffe06aa24c0
> > RBP: 0000000000625500 R08: 0000000000001c49 R09: 0000000000001c49
> > R10: 0000000000000000 R11: 0000000000000206 R12: 0000000001fd5fd0
> > R13: 0000000000000007 R14: 0000000001fc6250 R15: 0000000000000005
> > BUG: Bad page state in process udevd  pfn:2b13c
> > page:ffffea0000ac4f00 count:0 mapcount:0 mapping:ffff88800df2ad40 index:0xe
> > shmem_aops
> > flags: 0x1fffc000008000c(uptodate|dirty|swapbacked)
> > raw: 01fffc000008000c ffff8880a85af890 ffff8880a85af890 ffff88800df2ad40
> > raw: 000000000000000e 0000000000000000 00000000ffffffff 0000000000000000
> > page dumped because: non-NULL mapping
> > Modules linked in:
> > CPU: 1 PID: 7586 Comm: udevd Tainted: G    B              
> > 5.0.0-rc6-next-20190213 #34
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> > Google 01/01/2011
> > Call Trace:
> >   __dump_stack lib/dump_stack.c:77 [inline]
> >   dump_stack+0x172/0x1f0 lib/dump_stack.c:113
> >   bad_page.cold+0xda/0xff mm/page_alloc.c:586
> > name:"memfd:"
> >   free_pages_check_bad+0x142/0x1a0 mm/page_alloc.c:1014
> >   free_pages_check mm/page_alloc.c:1023 [inline]
> >   free_pages_prepare mm/page_alloc.c:1113 [inline]
> >   free_pcp_prepare mm/page_alloc.c:1138 [inline]
> >   free_unref_page_prepare mm/page_alloc.c:2991 [inline]
> >   free_unref_page_list+0x31d/0xc40 mm/page_alloc.c:3060
> >   release_pages+0x60d/0x1940 mm/swap.c:791
> >   pagevec_lru_move_fn+0x218/0x2a0 mm/swap.c:213
> >   __pagevec_lru_add mm/swap.c:917 [inline]
> >   lru_add_drain_cpu+0x2f7/0x520 mm/swap.c:581
> >   lru_add_drain+0x20/0x60 mm/swap.c:652
> >   exit_mmap+0x290/0x530 mm/mmap.c:3134
> >   __mmput kernel/fork.c:1047 [inline]
> >   mmput+0x15f/0x4c0 kernel/fork.c:1068
> >   exec_mmap fs/exec.c:1046 [inline]
> >   flush_old_exec+0x8d9/0x1c20 fs/exec.c:1279
> >   load_elf_binary+0x9bc/0x53f0 fs/binfmt_elf.c:864
> >   search_binary_handler fs/exec.c:1656 [inline]
> >   search_binary_handler+0x17f/0x570 fs/exec.c:1634
> >   exec_binprm fs/exec.c:1698 [inline]
> >   __do_execve_file.isra.0+0x1394/0x23f0 fs/exec.c:1818
> >   do_execveat_common fs/exec.c:1865 [inline]
> >   do_execve fs/exec.c:1882 [inline]
> >   __do_sys_execve fs/exec.c:1958 [inline]
> >   __se_sys_execve fs/exec.c:1953 [inline]
> >   __x64_sys_execve+0x8f/0xc0 fs/exec.c:1953
> >   do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
> >   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > RIP: 0033:0x7fc7001ba207
> > Code: Bad RIP value.
> > RSP: 002b:00007ffe06aa13b8 EFLAGS: 00000206 ORIG_RAX: 000000000000003b
> > RAX: ffffffffffffffda RBX: 00000000ffffffff RCX: 00007fc7001ba207
> > RDX: 0000000001fd5fd0 RSI: 00007ffe06aa14b0 RDI: 00007ffe06aa24c0
> > RBP: 0000000000625500 R08: 0000000000001c49 R09: 0000000000001c49
> > R10: 0000000000000000 R11: 0000000000000206 R12: 0000000001fd5fd0
> > R13: 0000000000000007 R14: 0000000001fc6250 R15: 0000000000000005
> > 
> > 
> > ---
> > This bug 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@xxxxxxxxxxxxxxxxx
> > 
> > syzbot will keep track of this bug report. See:
> > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
> > syzbot.
> > syzbot can test patches for this bug, for details see:
> > https://goo.gl/tpsmEJ#testing-patches
> 
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It's apparently the bug in the io_uring patchset I reported yesterday (well, I
stole it from another open syzbot bug...) and Jens is already planning to fix:
https://marc.info/?l=linux-api&m=155115288114046&w=2.  Reproducer is similar,
and the crash bisects down to the same commit from the io_uring patchset:
"block: implement bio helper to add iter bvec pages to bio".

- Eric