bisecting fixing commit since 14cfdbd39e316efd91ae6e403ef8211f0b022603 building syzkaller on 78267cec1aaa5e066d66e6a6c76fea1753e51b46 testing commit 14cfdbd39e316efd91ae6e403ef8211f0b022603 with gcc (GCC) 8.1.0 kernel signature: c21c8800eff7f312aa370efdd9798f8e363ebc30445050c5a1918869f72b1698 all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in generic_perform_write testing current HEAD 3fc898571b974f9a05e4e5c1fe17b18548207091 testing commit 3fc898571b974f9a05e4e5c1fe17b18548207091 with gcc (GCC) 8.1.0 kernel signature: f89a0d373ab6a09385861af67cb632abfb5c35a61727726413208a1977c4210a all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in generic_perform_write revisions tested: 2, total time: 26m4.323305861s (build: 18m5.16936418s, test: 6m58.86113891s) the crash still happens on HEAD commit msg: Linux 4.19.128 crash: BUG: unable to handle kernel NULL pointer dereference in generic_perform_write EXT4-fs (sda1): re-mounted. Opts: dax, EXT4-fs (sda1): DAX enabled. Warning: EXPERIMENTAL, use at your own risk EXT4-fs (sda1): warning: refusing change of dax flag with busy inodes while remounting EXT4-fs (sda1): re-mounted. Opts: dax, BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 PGD a9773067 P4D a9773067 PUD 8b2f0067 PMD 0 Oops: 0010 [#1] PREEMPT SMP KASAN CPU: 1 PID: 10531 Comm: syz-executor.1 Not tainted 4.19.128-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010: (null) Code: Bad RIP value. RSP: 0018:ffff88806f1479c8 EFLAGS: 00010246 RAX: ffffffff8738cb60 RBX: 0000000000000001 RCX: 0000000000000001 RDX: 0000000000000000 RSI: ffff88807fe6aa78 RDI: ffff88808eb6fd40 RBP: ffff88806f147b00 R08: 0000000000000000 R09: ffff88806f147a58 R10: ffffed1015d64732 R11: ffff8880aeb23993 R12: 0000000000000000 R13: ffff88806f147ad8 R14: ffff88807fe6aa78 R15: ffff88808fd5c140 FS: 00007ff19bd1c700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffffffffd6 CR3: 000000009619e000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: generic_perform_write+0x289/0x480 mm/filemap.c:3162 __generic_file_write_iter+0x201/0x580 mm/filemap.c:3287 ext4_file_write_iter+0x282/0xe60 fs/ext4/file.c:272 call_write_iter include/linux/fs.h:1821 [inline] new_sync_write fs/read_write.c:474 [inline] __vfs_write+0x443/0x890 fs/read_write.c:487 vfs_write+0x150/0x4d0 fs/read_write.c:549 ksys_write+0x103/0x260 fs/read_write.c:599 __do_sys_write fs/read_write.c:611 [inline] __se_sys_write fs/read_write.c:608 [inline] __x64_sys_write+0x6e/0xb0 fs/read_write.c:608 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45c849 Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ff19bd1bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007ff19bd1c6d4 RCX: 000000000045c849 RDX: 0000000000000001 RSI: 0000000020000080 RDI: 0000000000000003 RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000cdc R14: 00000000004cf01a R15: 000000000076bf0c Modules linked in: CR2: 0000000000000000 BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 ---[ end trace 5e144d7a0f8449c7 ]--- PGD 9fa76067 P4D 9fa76067 PUD 8c79d067 PMD 0 Oops: 0010 [#2] PREEMPT SMP KASAN CPU: 0 PID: 10535 Comm: syz-executor.0 Tainted: G D 4.19.128-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010: (null) Code: Bad RIP value. RSP: 0018:ffff88806fa7f9c8 EFLAGS: 00010246 RAX: ffffffff8738cb60 RBX: 0000000000000001 RCX: 0000000000000001 RDX: 0000000000000000 RSI: ffff88807ff023f8 RDI: ffff888099661840 RBP: ffff88806fa7fb00 R08: 0000000000000000 R09: ffff88806fa7fa58 RIP: 0010: (null) R10: ffffed10142d92c6 R11: ffff8880a16c9633 R12: 0000000000000000 R13: ffff88806fa7fad8 R14: ffff88807ff023f8 R15: ffff88808de8c100 FS: 00007f452a3ee700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffffffffd6 CR3: 0000000091bb0000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: generic_perform_write+0x289/0x480 mm/filemap.c:3162 __generic_file_write_iter+0x201/0x580 mm/filemap.c:3287 Code: Bad RIP value. ext4_file_write_iter+0x282/0xe60 fs/ext4/file.c:272 call_write_iter include/linux/fs.h:1821 [inline] new_sync_write fs/read_write.c:474 [inline] __vfs_write+0x443/0x890 fs/read_write.c:487 RSP: 0018:ffff88806f1479c8 EFLAGS: 00010246 vfs_write+0x150/0x4d0 fs/read_write.c:549 ksys_write+0x103/0x260 fs/read_write.c:599 RAX: ffffffff8738cb60 RBX: 0000000000000001 RCX: 0000000000000001 __do_sys_write fs/read_write.c:611 [inline] __se_sys_write fs/read_write.c:608 [inline] __x64_sys_write+0x6e/0xb0 fs/read_write.c:608 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RDX: 0000000000000000 RSI: ffff88807fe6aa78 RDI: ffff88808eb6fd40 RIP: 0033:0x45c849 Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f452a3edc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f452a3ee6d4 RCX: 000000000045c849 RDX: 0000000000000001 RSI: 0000000020000080 RDI: 0000000000000003 RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000cdc R14: 00000000004cf01a R15: 000000000076bf0c Modules linked in: CR2: 0000000000000000 RBP: ffff88806f147b00 R08: 0000000000000000 R09: ffff88806f147a58 EXT4-fs (sda1): DAX enabled. Warning: EXPERIMENTAL, use at your own risk EXT4-fs (sda1): warning: refusing change of dax flag with busy inodes while remounting R10: ffffed1015d64732 R11: ffff8880aeb23993 R12: 0000000000000000 EXT4-fs (sda1): re-mounted. Opts: dax, R13: ffff88806f147ad8 R14: ffff88807fe6aa78 R15: ffff88808fd5c140 EXT4-fs (sda1): DAX enabled. Warning: EXPERIMENTAL, use at your own risk FS: 00007ff19bd1c700(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 ---[ end trace 5e144d7a0f8449c8 ]--- CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffffffffd6 CR3: 000000009619e000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 RIP: 0010: (null)