[v5.15] Internal error in futex_lock_pi_atomic

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c79648372d02 Linux 5.15.189
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11553ea2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9e47345638b85bd0
dashboard link: https://syzkaller.appspot.com/bug?extid=a550340a47f5ff1fe7ff
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7ab49562317a/disk-c7964837.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e847ec1e38d3/vmlinux-c7964837.xz
kernel image: https://storage.googleapis.com/syzbot-assets/263158c6371c/Image-c7964837.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a55034...@syzkaller.appspotmail.com

Internal error: Oops - BTI: 0000000036000001 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 4722 Comm: syz.4.265 Not tainted 5.15.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
pstate: 42400405 (nZcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=jc)
pc : get_futex_value_locked kernel/futex/core.c:793 [inline]
pc : futex_lock_pi_atomic+0x170/0xea4 kernel/futex/core.c:1429
lr : __uaccess_mask_ptr arch/arm64/include/asm/uaccess.h:244 [inline]
lr : get_futex_value_locked kernel/futex/core.c:790 [inline]
lr : futex_lock_pi_atomic+0x14c/0xea4 kernel/futex/core.c:1429
sp : ffff80001fe67540
x29: ffff80001fe675c0 x28: ffff0000d99f9b40 x27: ffff80001fe677d0
x26: 1fffe0001b33f611 x25: ffff0000d99fb088 x24: 00000000fffffff2
x23: ffff80001fe677b8 x22: 0000000000000000 x21: dfff800000000000
x20: 0000000000000000 x19: ffff0000c0d36c00 x18: 0000000000000000
x17: ffff80000805b008 x16: ffff8000083c981c x15: ffff80000805b444
x14: ffff8000083c4470 x13: 1ffff0000282e06b x12: 0000000000080000
x11: 0000000000000309 x10: 0000000000000000 x9 : 0000ffffffffffff
x8 : 0000000000000000 x7 : ffff80000820263c x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000002
x2 : 0000000000000008 x1 : 0000000000000001 x0 : 0000000000000000
Call trace:
get_futex_value_locked kernel/futex/core.c:790 [inline]
futex_lock_pi_atomic+0x170/0xea4 kernel/futex/core.c:1429
futex_lock_pi+0x2d0/0x860 kernel/futex/core.c:3054
do_futex+0xb00/0x257c kernel/futex/core.c:-1
__do_sys_futex kernel/futex/core.c:4059 [inline]
__se_sys_futex kernel/futex/core.c:4040 [inline]
__arm64_sys_futex+0x388/0x400 kernel/futex/core.c:4040
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
Code: ea29011f 9a9f02ca d503229f b8400948 (2a1803e1)
---[ end trace bd3ecaf752ac121e ]---
----------------
Code disassembly (best guess):
0: ea29011f bics xzr, x8, x9
4: 9a9f02ca csel x10, x22, xzr, eq // eq = none
8: d503229f csdb
c: b8400948 ldtr w8, [x10]
* 10: 2a1803e1 mov w1, w24 <-- trapping instruction


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: c79648372d02 Linux 5.15.189
git tree: linux-5.15.y

console output: https://syzkaller.appspot.com/x/log.txt?x=112d3434580000

kernel config: https://syzkaller.appspot.com/x/.config?x=9e47345638b85bd0
dashboard link: https://syzkaller.appspot.com/bug?extid=a550340a47f5ff1fe7ff
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16430842580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=152d3434580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7ab49562317a/disk-c7964837.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e847ec1e38d3/vmlinux-c7964837.xz
kernel image: https://storage.googleapis.com/syzbot-assets/263158c6371c/Image-c7964837.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a55034...@syzkaller.appspotmail.com

Internal error: Oops - BTI: 0000000036000001 [#1] PREEMPT SMP
Modules linked in:

CPU: 1 PID: 4211 Comm: syz.0.17 Not tainted 5.15.189-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
pstate: 42400405 (nZcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=jc)
pc : get_futex_value_locked kernel/futex/core.c:793 [inline]
pc : futex_lock_pi_atomic+0x170/0xea4 kernel/futex/core.c:1429
lr : __uaccess_mask_ptr arch/arm64/include/asm/uaccess.h:244 [inline]
lr : get_futex_value_locked kernel/futex/core.c:790 [inline]
lr : futex_lock_pi_atomic+0x14c/0xea4 kernel/futex/core.c:1429

sp : ffff80001fd87540
x29: ffff80001fd875c0 x28: ffff0000d69951c0 x27: ffff80001fd877d0
x26: 1fffe0001ad32ce1 x25: ffff0000d6996708 x24: 00000000fffffff2
x23: ffff80001fd877b8 x22: 0000000000000000 x21: dfff800000000000
x20: 0000000000000000 x19: ffff0000c0d3c900 x18: 0000000000000000

x17: ffff80000805b008 x16: ffff8000083c981c x15: ffff80000805b444

x14: ffff8000083c4470 x13: 1ffff0000282e06b x12: 0000000000ff0100
x11: 0000000000000001 x10: 0000000000000000 x9 : 0000ffffffffffff

x8 : 0000000000000000 x7 : ffff80000820263c x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000002
x2 : 0000000000000008 x1 : 0000000000000001 x0 : 0000000000000000
Call trace:
get_futex_value_locked kernel/futex/core.c:790 [inline]
futex_lock_pi_atomic+0x170/0xea4 kernel/futex/core.c:1429
futex_lock_pi+0x2d0/0x860 kernel/futex/core.c:3054
do_futex+0xb00/0x257c kernel/futex/core.c:-1
__do_sys_futex kernel/futex/core.c:4059 [inline]
__se_sys_futex kernel/futex/core.c:4040 [inline]
__arm64_sys_futex+0x388/0x400 kernel/futex/core.c:4040
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
Code: ea29011f 9a9f02ca d503229f b8400948 (2a1803e1)

---[ end trace b782948f73b4102e ]---

----------------
Code disassembly (best guess):
0: ea29011f bics xzr, x8, x9
4: 9a9f02ca csel x10, x22, xzr, eq // eq = none
8: d503229f csdb
c: b8400948 ldtr w8, [x10]
* 10: 2a1803e1 mov w1, w24 <-- trapping instruction


---

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