On Wed, Dec 4, 2024 at 10:10 AM Jens Axboe <axboe@xxxxxxxxx> wrote: > > On 12/4/24 8:01 AM, Jens Axboe wrote: > > On 12/4/24 6:56 AM, syzbot wrote: > >> Hello, > >> > >> syzbot found the following issue on: > >> > >> HEAD commit: c245a7a79602 Add linux-next specific files for 20241203 > >> git tree: linux-next > >> console+strace: https://syzkaller.appspot.com/x/log.txt?x=10ae840f980000 > >> kernel config: https://syzkaller.appspot.com/x/.config?x=af3fe1d01b9e7b7 > >> dashboard link: https://syzkaller.appspot.com/bug?extid=092bbab7da235a02a03a > >> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14a448df980000 > >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15cca330580000 > >> > >> Downloadable assets: > >> disk image: https://storage.googleapis.com/syzbot-assets/8cc90a2ea120/disk-c245a7a7.raw.xz > >> vmlinux: https://storage.googleapis.com/syzbot-assets/0f6b1a1a0541/vmlinux-c245a7a7.xz > >> kernel image: https://storage.googleapis.com/syzbot-assets/9fa3eac09ddc/bzImage-c245a7a7.xz > >> > >> IMPORTANT: if you fix the issue, please add the following tag to the commit: > >> Reported-by: syzbot+092bbab7da235a02a03a@xxxxxxxxxxxxxxxxxxxxxxxxx > >> > >> ================================================================== > >> BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:96 [inline] > >> BUG: KASAN: null-ptr-deref in atomic_long_sub_and_test include/linux/atomic/atomic-instrumented.h:4521 [inline] > >> BUG: KASAN: null-ptr-deref in put_cred_many include/linux/cred.h:255 [inline] > >> BUG: KASAN: null-ptr-deref in put_cred include/linux/cred.h:269 [inline] > >> BUG: KASAN: null-ptr-deref in io_unregister_personality io_uring/register.c:82 [inline] > >> BUG: KASAN: null-ptr-deref in __io_uring_register io_uring/register.c:698 [inline] > >> BUG: KASAN: null-ptr-deref in __do_sys_io_uring_register io_uring/register.c:902 [inline] > >> BUG: KASAN: null-ptr-deref in __se_sys_io_uring_register+0x1227/0x3b60 io_uring/register.c:879 > >> Write of size 8 at addr 0000000000000406 by task syz-executor274/5828 > >> > >> CPU: 1 UID: 0 PID: 5828 Comm: syz-executor274 Not tainted 6.13.0-rc1-next-20241203-syzkaller #0 > >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 > >> Call Trace: > >> <TASK> > >> __dump_stack lib/dump_stack.c:94 [inline] > >> dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 > >> print_report+0xe8/0x550 mm/kasan/report.c:492 > >> kasan_report+0x143/0x180 mm/kasan/report.c:602 > >> kasan_check_range+0x282/0x290 mm/kasan/generic.c:189 > >> instrument_atomic_read_write include/linux/instrumented.h:96 [inline] > >> atomic_long_sub_and_test include/linux/atomic/atomic-instrumented.h:4521 [inline] > >> put_cred_many include/linux/cred.h:255 [inline] > >> put_cred include/linux/cred.h:269 [inline] > >> io_unregister_personality io_uring/register.c:82 [inline] > >> __io_uring_register io_uring/register.c:698 [inline] > >> __do_sys_io_uring_register io_uring/register.c:902 [inline] > >> __se_sys_io_uring_register+0x1227/0x3b60 io_uring/register.c:879 > >> do_syscall_x64 arch/x86/entry/common.c:52 [inline] > >> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 > >> entry_SYSCALL_64_after_hwframe+0x77/0x7f > >> RIP: 0033:0x7f65bbcb03a9 > >> Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > >> RSP: 002b:00007ffe8fac7478 EFLAGS: 00000246 ORIG_RAX: 00000000000001ab > >> RAX: ffffffffffffffda RBX: 000000000000371d RCX: 00007f65bbcb03a9 > >> RDX: 0000000000000000 RSI: 000000000000000a RDI: 0000000000000003 > >> RBP: 0000000000000003 R08: 00000000000ac5f8 R09: 00000000000ac5f8 > >> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 > >> R13: 00007ffe8fac7648 R14: 0000000000000001 R15: 0000000000000001 > >> </TASK> > >> ================================================================== > > > > Not sure what's going on with -next, but this looks like nonsense - we > > store a valid pointer in the xarry, and then attempt to delete an > > invalid index which then returns a totally garbage pointer!? I'll check > > what is in -next, but this very much does not look like an io_uring > > issue. > > Took a quick look, and it's this patch: > > commit d2e88c71bdb07f1e5ccffbcc80d747ccd6144b75 > Author: Tamir Duberstein <tamird@xxxxxxxxx> > Date: Tue Nov 12 14:25:37 2024 -0500 > > xarray: extract helper from __xa_{insert,cmpxchg} > > in the current -next tree. Adding a few folks who might be interested. > > -- > Jens Axboe Yep, looks broken. I believe the missing bit is diff --git a/lib/xarray.c b/lib/xarray.c index 2af86bede3c1..5da8d18899a1 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1509,7 +1509,7 @@ static void *xas_result(struct xa_state *xas, void *curr) void *__xa_erase(struct xarray *xa, unsigned long index) { XA_STATE(xas, xa, index); - return xas_result(&xas, xas_store(&xas, NULL)); + return xas_result(&xas, xa_zero_to_null(xas_store(&xas, NULL))); } EXPORT_SYMBOL(__xa_erase); This would explain deletion of a reserved entry returning `XA_ZERO_ENTRY` rather than `NULL`. My apologies for this breakage. Should I send a new version? A new "fixes" patch? tamird
