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Date:   Wed, 13 Feb 2019 12:23:31 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     syzbot <syzbot+2cd2887ea471ed6e6995@...kaller.appspotmail.com>
Cc:     dan.j.williams@...el.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, mhocko@...e.com, nborisov@...e.com,
        rppt@...ux.vnet.ibm.com, shakeelb@...gle.com,
        syzkaller-bugs@...glegroups.com, vbabka@...e.cz,
        willy@...radead.org, joel@...lfernandes.org,
        Mike Kravetz <kravetz@...ibm.com>
Subject: Re: BUG: Bad page state (5)

On Wed, 13 Feb 2019 09:56:04 -0800 syzbot <syzbot+2cd2887ea471ed6e6995@...kaller.appspotmail.com> 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@...kaller.appspotmail.com

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@...glegroups.com.
> 
> 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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