Re: [syzbot] [mm?] WARNING in unmap_page_range (2)
From: Andrew Morton
Date: Wed Nov 15 2023 - 17:00:12 EST
On Wed, 15 Nov 2023 05:32:19 -0800 syzbot <syzbot+7ca4b2719dc742b8d0a4@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: ac347a0655db Merge tag 'arm64-fixes' of git://git.kernel.o..
> git tree: upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=15ff3057680000
> kernel config: https://syzkaller.appspot.com/x/.config?x=287570229f5c0a7c
> dashboard link: https://syzkaller.appspot.com/bug?extid=7ca4b2719dc742b8d0a4
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=162a25ff680000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13d62338e80000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/00e30e1a5133/disk-ac347a06.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/07c43bc37935/vmlinux-ac347a06.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/c6690c715398/bzImage-ac347a06.xz
>
> The issue was bisected to:
>
> commit 12f6b01a0bcbeeab8cc9305673314adb3adf80f7
> Author: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
> Date: Mon Aug 21 14:15:15 2023 +0000
>
> fs/proc/task_mmu: add fast paths to get/clear PAGE_IS_WRITTEN flag
Thanks. The bisection is surprising, but the mentioned patch does
mess with pagemap.
How about we add this?
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: mm/memory.c:zap_pte_range() print bad swap entry
Date: Wed Nov 15 01:54:18 PM PST 2023
We have a report of this WARN() triggering. Let's print the offending
swp_entry_t to help diagnosis.
Link: https://lkml.kernel.org/r/000000000000b0e576060a30ee3b@xxxxxxxxxx
Cc: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 1 +
1 file changed, 1 insertion(+)
--- a/mm/memory.c~a
+++ a/mm/memory.c
@@ -1521,6 +1521,7 @@ static unsigned long zap_pte_range(struc
continue;
} else {
/* We should have covered all the swap entry types */
+ pr_alert("unrecognized swap entry 0x%lx\n", entry.val);
WARN_ON_ONCE(1);
}
pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
_