linux-kernel - Re: mm: Unable to handle kernel NULL pointer dereference at virtual address - mmap_region (include/linux/fs.h:580 mm/mmap.c:2946)

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Message-ID: <48534660-d5f7-45b2-8f99-19c8fb3e51c8@lucifer.local>
Date:   Mon, 16 Oct 2023 12:05:37 +0100
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     Naresh Kamboju <naresh.kamboju@...aro.org>
Cc:     open list <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, lkft-triage@...ts.linaro.org,
        "Reviewed-by: Jan Kara" <jack@...e.cz>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Hugh Dickins <hughd@...gle.com>, willy@...radead.org,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Carpenter <dan.carpenter@...aro.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: mm: Unable to handle kernel NULL pointer dereference at virtual
 address - mmap_region (include/linux/fs.h:580 mm/mmap.c:2946)

On Mon, Oct 16, 2023 at 03:52:07PM +0530, Naresh Kamboju wrote:
> Following kernel crash noticed while running LTP hugetlb and selftests on
> qemu-x86_64 and qemu-arm64 running with Linux next 6.6.0-rc6-next-20231016.
>
> Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
> Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
>
> Test Logs:
> -----

[snip]

> <4>[   97.499871] Call trace:
> <4>[ 97.500288] mmap_region (include/linux/fs.h:580 mm/mmap.c:2946)

OK this is from a patch of mine, and an easy fix (incorrect assumption about
vm->vm_file == file).

I will put a fix forward tonight.

> <4>[ 97.500814] do_mmap (mm/mmap.c:1379)
> <4>[ 97.501243] vm_mmap_pgoff (mm/util.c:546)
> <4>[ 97.501711] ksys_mmap_pgoff (mm/mmap.c:1425)
> <4>[ 97.502166] __arm64_sys_mmap (arch/arm64/kernel/sys.c:21)
> <4>[ 97.502634] invoke_syscall (arch/arm64/include/asm/current.h:19
> arch/arm64/kernel/syscall.c:56)
> <4>[ 97.503175] el0_svc_common.constprop.0
> (include/linux/thread_info.h:127 (discriminator 2)
> arch/arm64/kernel/syscall.c:144 (discriminator 2))
> <4>[ 97.503763] do_el0_svc (arch/arm64/kernel/syscall.c:156)
> <4>[ 97.504191] el0_svc (arch/arm64/include/asm/daifflags.h:28
> arch/arm64/kernel/entry-common.c:133
> arch/arm64/kernel/entry-common.c:144
> arch/arm64/kernel/entry-common.c:679)

[snip]