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Message-ID: <CAJD7tkYrRAK7rjfyArbdq8=Y6CV-T_YbL+SvBEGU8_MV3opbqg@mail.gmail.com>
Date: Tue, 30 Apr 2024 01:32:30 -0700
From: Yosry Ahmed <yosryahmed@...gle.com>
To: syzbot <syzbot+9c9d60f1b20b22ce218a@...kaller.appspotmail.com>
Cc: akpm@...ux-foundation.org, chengming.zhou@...ux.dev, hannes@...xchg.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org, nphamcs@...il.com,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] KMSAN: uninit-value in zswap_rb_insert
On Mon, Apr 29, 2024 at 11:02 PM syzbot
<syzbot+9c9d60f1b20b22ce218a@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: e33c4963bf53 Merge tag 'nfsd-6.9-5' of git://git.kernel.or..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=123d5a0f180000
> kernel config: https://syzkaller.appspot.com/x/.config?x=776c05250f36d55c
> dashboard link: https://syzkaller.appspot.com/bug?extid=9c9d60f1b20b22ce218a
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/a10175188ebb/disk-e33c4963.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/abe743417d16/vmlinux-e33c4963.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/fb10cccc9909/bzImage-e33c4963.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+9c9d60f1b20b22ce218a@...kaller.appspotmail.com
>
> =====================================================
> BUG: KMSAN: uninit-value in zswap_rb_insert+0x1e9/0x330 mm/zswap.c:842
I am not sure how this could happen. The report is complaining about
the access in the loop condition AFAICT:
while (*link) { /* here */
.
}
*link should start as root->rb_node (which should be NULL as it is
static data), then be updated to point at a zswap_entry->rbnode as
entries get added. *link should keep then be updated to values at
zswap_entry->rbnode->{left/right}.
Although entry->rbnode->{left/right} are not initialized when
allocated by zswap_entry_cache_alloc() as the report mentions, they
are initialized in zswap_rb_insert()->rb_link_node() when they are
added to the tree.
Also, this code is removed with the xarray conversion anyway.
> zswap_rb_insert+0x1e9/0x330 mm/zswap.c:842
> zswap_store+0x22f2/0x2ca0 mm/zswap.c:1591
> swap_writepage+0x126/0x4c0 mm/page_io.c:198
> pageout mm/vmscan.c:660 [inline]
> shrink_folio_list+0x4a55/0x7910 mm/vmscan.c:1323
> evict_folios+0x9d7f/0xcc20 mm/vmscan.c:4537
> try_to_shrink_lruvec+0x160e/0x1a50 mm/vmscan.c:4733
> shrink_one+0x66f/0xd40 mm/vmscan.c:4772
> shrink_many mm/vmscan.c:4835 [inline]
> lru_gen_shrink_node mm/vmscan.c:4935 [inline]
> shrink_node+0x4856/0x55f0 mm/vmscan.c:5894
> shrink_zones mm/vmscan.c:6152 [inline]
> do_try_to_free_pages+0x820/0x2570 mm/vmscan.c:6214
> try_to_free_pages+0xb7b/0x1820 mm/vmscan.c:6449
> __perform_reclaim mm/page_alloc.c:3774 [inline]
> __alloc_pages_direct_reclaim mm/page_alloc.c:3796 [inline]
> __alloc_pages_slowpath+0x1035/0x31a0 mm/page_alloc.c:4202
> __alloc_pages+0xacf/0xe70 mm/page_alloc.c:4588
> alloc_pages_mpol+0x299/0x990 mm/mempolicy.c:2264
> vma_alloc_folio+0x418/0x680 mm/mempolicy.c:2303
> do_cow_fault mm/memory.c:4918 [inline]
> do_fault mm/memory.c:5026 [inline]
> do_pte_missing mm/memory.c:3880 [inline]
> handle_pte_fault mm/memory.c:5300 [inline]
> __handle_mm_fault mm/memory.c:5441 [inline]
> handle_mm_fault+0x4f2f/0xce00 mm/memory.c:5606
> do_user_addr_fault arch/x86/mm/fault.c:1413 [inline]
> handle_page_fault arch/x86/mm/fault.c:1505 [inline]
> exc_page_fault+0x2a0/0x730 arch/x86/mm/fault.c:1563
> asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:623
> rep_stos_alternative+0x40/0x80 arch/x86/lib/clear_page_64.S:92
> load_elf_binary+0x212e/0x4d30 fs/binfmt_elf.c:1132
> search_binary_handler fs/exec.c:1778 [inline]
> exec_binprm fs/exec.c:1820 [inline]
> bprm_execve+0xc57/0x21c0 fs/exec.c:1872
> do_execveat_common+0xceb/0xd70 fs/exec.c:1979
> do_execve fs/exec.c:2053 [inline]
> __do_sys_execve fs/exec.c:2129 [inline]
> __se_sys_execve fs/exec.c:2124 [inline]
> __x64_sys_execve+0xf4/0x130 fs/exec.c:2124
> x64_sys_call+0x1612/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:60
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Uninit was created at:
> __alloc_pages+0x9d6/0xe70 mm/page_alloc.c:4598
> __alloc_pages_node include/linux/gfp.h:238 [inline]
> alloc_pages_node include/linux/gfp.h:261 [inline]
> alloc_slab_page mm/slub.c:2175 [inline]
> allocate_slab mm/slub.c:2338 [inline]
> new_slab+0x2de/0x1400 mm/slub.c:2391
> ___slab_alloc+0x1184/0x33d0 mm/slub.c:3525
> __slab_alloc mm/slub.c:3610 [inline]
> __slab_alloc_node mm/slub.c:3663 [inline]
> slab_alloc_node mm/slub.c:3835 [inline]
> kmem_cache_alloc_node+0x6ea/0xc50 mm/slub.c:3888
> zswap_entry_cache_alloc mm/zswap.c:874 [inline]
> zswap_store+0xb26/0x2ca0 mm/zswap.c:1535
> swap_writepage+0x126/0x4c0 mm/page_io.c:198
> pageout mm/vmscan.c:660 [inline]
> shrink_folio_list+0x4a55/0x7910 mm/vmscan.c:1323
> evict_folios+0x9d7f/0xcc20 mm/vmscan.c:4537
> try_to_shrink_lruvec+0x160e/0x1a50 mm/vmscan.c:4733
> shrink_one+0x66f/0xd40 mm/vmscan.c:4772
> shrink_many mm/vmscan.c:4835 [inline]
> lru_gen_shrink_node mm/vmscan.c:4935 [inline]
> shrink_node+0x4856/0x55f0 mm/vmscan.c:5894
> shrink_zones mm/vmscan.c:6152 [inline]
> do_try_to_free_pages+0x820/0x2570 mm/vmscan.c:6214
> try_to_free_pages+0xb7b/0x1820 mm/vmscan.c:6449
> __perform_reclaim mm/page_alloc.c:3774 [inline]
> __alloc_pages_direct_reclaim mm/page_alloc.c:3796 [inline]
> __alloc_pages_slowpath+0x1035/0x31a0 mm/page_alloc.c:4202
> __alloc_pages+0xacf/0xe70 mm/page_alloc.c:4588
> alloc_pages_mpol+0x299/0x990 mm/mempolicy.c:2264
> alloc_pages+0x1bf/0x1e0 mm/mempolicy.c:2335
> vm_area_alloc_pages mm/vmalloc.c:3561 [inline]
> __vmalloc_area_node mm/vmalloc.c:3637 [inline]
> __vmalloc_node_range+0x100a/0x28b0 mm/vmalloc.c:3818
> vmalloc_user+0x90/0xb0 mm/vmalloc.c:3972
> kcov_ioctl+0x5d/0x660 kernel/kcov.c:704
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:904 [inline]
> __se_sys_ioctl+0x261/0x450 fs/ioctl.c:890
> __x64_sys_ioctl+0x96/0xe0 fs/ioctl.c:890
> x64_sys_call+0x1883/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:17
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> CPU: 0 PID: 5281 Comm: dhcpcd-run-hook Not tainted 6.9.0-rc5-syzkaller-00053-ge33c4963bf53 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
> =====================================================
>
>
> ---
> 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@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
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