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In-Reply-To: <20260323162617.2421-1-jack@suse.cz> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69c1c09b.a70a0220.59f55.0001.GAE@google.com> Subject: [syzbot ci] Re: udf: Fix race between file type conversion and writeback From: syzbot ci To: jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, luckd0g@163.com Cc: syzbot@lists.linux.dev, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot ci has tested the following series [v1] udf: Fix race between file type conversion and writeback https://lore.kernel.org/all/20260323162617.2421-1-jack@suse.cz * [PATCH 1/2] writeback: Export folio_prepare_writeback() * [PATCH 2/2] udf: Fix race between file type conversion and writeback and found the following issue: general protection fault in folio_prepare_writeback Full report is available here: https://ci.syzbot.org/series/03e405d8-f247-471a-8469-f544c8393300 *** general protection fault in folio_prepare_writeback tree: mm-new URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/akpm/mm.git base: af5802cff33fe3c557dff87cd3897d14241a7c6d arch: amd64 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 config: https://ci.syzbot.org/builds/d1944db2-4f63-4e26-b642-d71f55382c9d/config C repro: https://ci.syzbot.org/findings/87b82667-f800-480e-b52a-38decce9e6c4/c_repro syz repro: https://ci.syzbot.org/findings/87b82667-f800-480e-b52a-38decce9e6c4/syz_repro Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] CPU: 0 UID: 0 PID: 1860 Comm: kworker/u9:3 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Workqueue: writeback wb_workfn (flush-7:0) RIP: 0010:folio_prepare_writeback+0x32/0x280 mm/page-writeback.c:2371 Code: 56 41 55 41 54 53 50 48 89 d3 48 89 f5 49 89 fe 49 bd 00 00 00 00 00 fc ff df e8 f9 22 c2 ff 4c 8d 63 18 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 ef 6a 2c 00 4d 39 34 24 0f 85 bf RSP: 0018:ffffc9000901f1e8 EFLAGS: 00010203 RAX: 0000000000000002 RBX: fffffffffffffffe RCX: ffff88810981ba80 RDX: 0000000000000000 RSI: ffffc9000901f4e0 RDI: ffff8881a659bc48 RBP: ffffc9000901f4e0 R08: ffff88810981ba80 R09: 0000000000000003 R10: 0000000000000406 R11: 0000000000000000 R12: 0000000000000016 R13: dffffc0000000000 R14: ffff8881a659bc48 R15: ffffc9000901f4e0 FS: 0000000000000000(0000) GS:ffff88818de5e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00001b4fda9cd4b8 CR3: 0000000110906000 CR4: 00000000000006f0 Call Trace: udf_writepages+0xce/0x3b0 fs/udf/inode.c:205 do_writepages+0x32e/0x550 mm/page-writeback.c:2554 __writeback_single_inode+0x133/0x11a0 fs/fs-writeback.c:1750 writeback_sb_inodes+0x992/0x1a20 fs/fs-writeback.c:2042 wb_writeback+0x456/0xb70 fs/fs-writeback.c:2227 wb_do_writeback fs/fs-writeback.c:2374 [inline] wb_workfn+0x414/0xf50 fs/fs-writeback.c:2414 process_one_work kernel/workqueue.c:3276 [inline] process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:folio_prepare_writeback+0x32/0x280 mm/page-writeback.c:2371 Code: 56 41 55 41 54 53 50 48 89 d3 48 89 f5 49 89 fe 49 bd 00 00 00 00 00 fc ff df e8 f9 22 c2 ff 4c 8d 63 18 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 e7 e8 ef 6a 2c 00 4d 39 34 24 0f 85 bf RSP: 0018:ffffc9000901f1e8 EFLAGS: 00010203 RAX: 0000000000000002 RBX: fffffffffffffffe RCX: ffff88810981ba80 RDX: 0000000000000000 RSI: ffffc9000901f4e0 RDI: ffff8881a659bc48 RBP: ffffc9000901f4e0 R08: ffff88810981ba80 R09: 0000000000000003 R10: 0000000000000406 R11: 0000000000000000 R12: 0000000000000016 R13: dffffc0000000000 R14: ffff8881a659bc48 R15: ffffc9000901f4e0 FS: 0000000000000000(0000) GS:ffff8882a945e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00001b4fda9c7570 CR3: 0000000173314000 CR4: 00000000000006f0 ---------------- Code disassembly (best guess): 0: 56 push %rsi 1: 41 55 push %r13 3: 41 54 push %r12 5: 53 push %rbx 6: 50 push %rax 7: 48 89 d3 mov %rdx,%rbx a: 48 89 f5 mov %rsi,%rbp d: 49 89 fe mov %rdi,%r14 10: 49 bd 00 00 00 00 00 movabs $0xdffffc0000000000,%r13 17: fc ff df 1a: e8 f9 22 c2 ff call 0xffc22318 1f: 4c 8d 63 18 lea 0x18(%rbx),%r12 23: 4c 89 e0 mov %r12,%rax 26: 48 c1 e8 03 shr $0x3,%rax * 2a: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction 2f: 74 08 je 0x39 31: 4c 89 e7 mov %r12,%rdi 34: e8 ef 6a 2c 00 call 0x2c6b28 39: 4d 39 34 24 cmp %r14,(%r12) 3d: 0f .byte 0xf 3e: 85 .byte 0x85 3f: bf .byte 0xbf *** If these findings have caused you to resend the series or submit a separate fix, please add the following tag to your commit message: Tested-by: syzbot@syzkaller.appspotmail.com --- This report is generated by a bot. It may contain errors. syzbot ci engineers can be reached at syzkaller@googlegroups.com.