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Mon, 24 Apr 2023 01:28:28 -0700 (PDT) MIME-Version: 1.0 References: <0000000000001db82205fa108b35@google.com> In-Reply-To: <0000000000001db82205fa108b35@google.com> From: Dmitry Vyukov Date: Mon, 24 Apr 2023 10:28:15 +0200 Message-ID: Subject: Re: [syzbot] [mm?] KCSAN: data-race in generic_fillattr / shmem_unlink (3) To: syzbot Cc: akpm@linux-foundation.org, hughd@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: DB4C21A0006 X-Stat-Signature: gcpec8j71qi4mux6hs3yu94i3qirudda X-Rspam-User: X-HE-Tag: 1682324909-139428 X-HE-Meta: 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 IyHaenvw 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 V0usSJv3 aQZk2nRsETWVD8n9JYJp/bH7TncSZ6zZmlC/aqjqyOc+0QFl3Ywx5djAOEsa6QmXORPWSjKpaVui4DKIlGUFaVMHO12BBtt2 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 24 Apr 2023 at 10:10, syzbot wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: cb0856346a60 Merge tag 'mm-hotfixes-stable-2023-04-19-16-3.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=10b9e8bfc80000 > kernel config: https://syzkaller.appspot.com/x/.config?x=fa4baf7c6b35b5d5 > dashboard link: https://syzkaller.appspot.com/bug?extid=f682b67a78ce05867e78 > compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/a02dd7789fb2/disk-cb085634.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/a1a1eac454f6/vmlinux-cb085634.xz > kernel image: https://storage.googleapis.com/syzbot-assets/bb0447014913/bzImage-cb085634.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+f682b67a78ce05867e78@syzkaller.appspotmail.com I think shmem_unlink() needs to use i_size_write() to update the size. Writes to i_size are not assumed to be atomic throughout the kernel code. > ================================================================== > BUG: KCSAN: data-race in generic_fillattr / shmem_unlink > > read-write to 0xffff888104d167b8 of 8 bytes by task 23887 on cpu 1: > shmem_unlink+0x102/0x190 mm/shmem.c:3036 > vfs_unlink+0x261/0x3e0 fs/namei.c:4250 > do_unlinkat+0x266/0x4f0 fs/namei.c:4316 > __do_sys_unlink fs/namei.c:4364 [inline] > __se_sys_unlink fs/namei.c:4362 [inline] > __x64_sys_unlink+0x30/0x40 fs/namei.c:4362 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > read to 0xffff888104d167b8 of 8 bytes by task 27823 on cpu 0: > i_size_read include/linux/fs.h:866 [inline] > generic_fillattr+0x13f/0x1e0 fs/stat.c:58 > shmem_getattr+0x32a/0x3b0 mm/shmem.c:1068 > vfs_getattr_nosec+0x1e3/0x3c0 fs/stat.c:133 > vfs_getattr fs/stat.c:170 [inline] > vfs_statx+0x156/0x300 fs/stat.c:242 > vfs_fstatat fs/stat.c:276 [inline] > __do_sys_newfstatat fs/stat.c:446 [inline] > __se_sys_newfstatat+0x8a/0x2a0 fs/stat.c:440 > __x64_sys_newfstatat+0x55/0x60 fs/stat.c:440 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > value changed: 0x00000000000000c8 -> 0x00000000000000b4 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 0 PID: 27823 Comm: udevd Not tainted 6.3.0-rc7-syzkaller-00089-gcb0856346a60 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023 > ================================================================== > > > --- > 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@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/0000000000001db82205fa108b35%40google.com.