(cc James, Al, Christian) Please see the splat below. The NULL dereference is due to get_cred() in alloc_fs_context() attempting to increment current->cred->usage while current->cred == NULL, and this is a result of the fact that PM notifier call chain is called while the task is exiting. IIRC, the intent was for commit 11092db5b573 efivarfs: fix NULL dereference on resume to be replaced at some point with something more robust; might that address this issue as well? Thanks, Ard. On Sun, 11 May 2025 at 19:44, syzbot <syzbot+52cd651546d11d2af06b@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: c32f8dc5aaf9 Merge branch 'for-next/core' into for-kernelci > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci > console output: https://syzkaller.appspot.com/x/log.txt?x=1762d670580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=ea4635ffd6ad5b4a > dashboard link: https://syzkaller.appspot.com/bug?extid=52cd651546d11d2af06b > compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2 > userspace arch: arm64 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=165c0cd4580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16f49cf4580000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/b921498959d4/disk-c32f8dc5.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/04e6ad946c4b/vmlinux-c32f8dc5.xz > kernel image: https://storage.googleapis.com/syzbot-assets/d4f0d8db50ee/Image-c32f8dc5.gz.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+52cd651546d11d2af06b@xxxxxxxxxxxxxxxxxxxxxxxxx > > efivarfs: resyncing variable state > Unable to handle kernel paging request at virtual address dfff800000000005 > KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] > Mem abort info: > ESR = 0x0000000096000005 > EC = 0x25: DABT (current EL), IL = 32 bits > SET = 0, FnV = 0 > EA = 0, S1PTW = 0 > FSC = 0x05: level 1 translation fault > Data abort info: > ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 > CM = 0, WnR = 0, TnD = 0, TagAccess = 0 > GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 > [dfff800000000005] address between user and kernel address ranges > Internal error: Oops: 0000000096000005 [#1] SMP > Modules linked in: > CPU: 1 UID: 0 PID: 6487 Comm: syz-executor120 Not tainted 6.15.0-rc5-syzkaller-gc32f8dc5aaf9 #0 PREEMPT > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 > pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : alloc_fs_context+0x1b4/0x76c fs/fs_context.c:294 > lr : __lse_atomic64_add arch/arm64/include/asm/atomic_lse.h:134 [inline] > lr : arch_atomic64_add arch/arm64/include/asm/atomic.h:67 [inline] > lr : raw_atomic64_add include/linux/atomic/atomic-arch-fallback.h:2672 [inline] > lr : raw_atomic_long_add include/linux/atomic/atomic-long.h:121 [inline] > lr : atomic_long_add include/linux/atomic/atomic-instrumented.h:3261 [inline] > lr : get_cred_many include/linux/cred.h:203 [inline] > lr : get_cred include/linux/cred.h:218 [inline] > lr : alloc_fs_context+0x150/0x76c fs/fs_context.c:293 > sp : ffff8000a31b7760 > x29: ffff8000a31b7790 x28: dfff800000000000 x27: ffff0000c8ef88d8 > x26: 0000000000000028 x25: ffff0000c7e6f4c8 x24: ffff80008fb953e0 > x23: 0000000000000000 x22: ffff0000c7e6f498 x21: ffff0000c8ef8000 > x20: 0000000000000000 x19: ffff0000c7e6f400 x18: 00000000ffffffff > x17: ffff800092f27000 x16: ffff80008adb31c0 x15: 0000000000000001 > x14: 1fffe0001a05b0e0 x13: 0000000000000000 x12: 0000000000000000 > x11: ffff60001a05b0e1 x10: 0000000000ff0100 x9 : 0000000000000000 > x8 : 0000000000000005 x7 : ffff80008022b2b8 x6 : ffff80008022b4b4 > x5 : ffff0000dabc9c90 x4 : ffff8000a31b7520 x3 : ffff800080dfa950 > x2 : 0000000000000001 x1 : 0000000000000008 x0 : 0000000000000001 > Call trace: > alloc_fs_context+0x1b4/0x76c fs/fs_context.c:294 (P) > fs_context_for_mount+0x34/0x44 fs/fs_context.c:332 > vfs_kern_mount+0x38/0x178 fs/namespace.c:1313 > efivarfs_pm_notify+0x1c4/0x4b4 fs/efivarfs/super.c:529 > notifier_call_chain+0x1b8/0x4e4 kernel/notifier.c:85 > blocking_notifier_call_chain+0x70/0xa0 kernel/notifier.c:380 > pm_notifier_call_chain+0x2c/0x3c kernel/power/main.c:109 > snapshot_release+0x104/0x1c4 kernel/power/user.c:125 > __fput+0x340/0x75c fs/file_table.c:465 > ____fput+0x20/0x58 fs/file_table.c:493 > task_work_run+0x1dc/0x260 kernel/task_work.c:227 > exit_task_work include/linux/task_work.h:40 [inline] > do_exit+0x4e8/0x1998 kernel/exit.c:953 > do_group_exit+0x194/0x22c kernel/exit.c:1102 > __do_sys_exit_group kernel/exit.c:1113 [inline] > __se_sys_exit_group kernel/exit.c:1111 [inline] > pid_child_should_wake+0x0/0x1dc kernel/exit.c:1111 > __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] > invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 > el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 > do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 > el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767 > el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786 > el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 > Code: 97f8a879 f9400368 9100a11a d343ff48 (387c6908) > ---[ end trace 0000000000000000 ]--- > ---------------- > Code disassembly (best guess): > 0: 97f8a879 bl 0xffffffffffe2a1e4 > 4: f9400368 ldr x8, [x27] > 8: 9100a11a add x26, x8, #0x28 > c: d343ff48 lsr x8, x26, #3 > * 10: 387c6908 ldrb w8, [x8, x28] <-- trapping instruction > > > --- > 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@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > If the report is already addressed, let syzbot know by replying with: > #syz fix: exact-commit-title > > If you want syzbot to run the reproducer, reply with: > #syz test: git://repo/address.git branch-or-commit-hash > If you attach or paste a git patch, syzbot will apply it before testing. > > If you want to overwrite report's subsystems, reply with: > #syz set subsystems: new-subsystem > (See the list of subsystem names on the web dashboard) > > If the report is a duplicate of another one, reply with: > #syz dup: exact-subject-of-another-report > > If you want to undo deduplication, reply with: > #syz undup
