[syzbot] [bpf?] KMSAN: uninit-value in handle_bug

[syzbot] [bpf?] KMSAN: uninit-value in handle_bug

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    cc25df3e2e22 Merge tag 'for-6.19/block-20251201' of git://..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16c2eab4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6c445efc9db431cb
dashboard link: https://syzkaller.appspot.com/bug?extid=ba80855313e6fa65717a
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a1afac06cfc1/disk-cc25df3e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7bd5369ac00a/vmlinux-cc25df3e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e183dedd04c6/bzImage-cc25df3e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ba80855313e6fa65717a@syzkaller.appspotmail.com

------------[ cut here ]------------
=====================================================
BUG: KMSAN: uninit-value in vsnprintf+0x15d9/0x1b30 lib/vsprintf.c:2911
 vsnprintf+0x15d9/0x1b30 lib/vsprintf.c:2911
 vprintk_store+0x3ae/0x1530 kernel/printk/printk.c:2255
 vprintk_emit+0x27b/0xc50 kernel/printk/printk.c:2402
 vprintk_default+0x3f/0x50 kernel/printk/printk.c:2441
 vprintk+0x36/0x50 kernel/printk/printk_safe.c:82
 __warn_printf lib/bug.c:187 [inline]
 __report_bug+0xa53/0xe80 lib/bug.c:240
 report_bug_entry+0x148/0x1d0 lib/bug.c:265
 handle_bug+0xe1/0x230 arch/x86/kernel/traps.c:430
 exc_invalid_op+0x1f/0x50 arch/x86/kernel/traps.c:489
 asm_exc_invalid_op+0x1f/0x30 arch/x86/include/asm/idtentry.h:616
 reg_bounds_sanity_check+0x577/0x1450 kernel/bpf/verifier.c:2742
 reg_set_min_max+0x3be/0x450 kernel/bpf/verifier.c:16572
 check_cond_jmp_op+0x3a87/0x5380 kernel/bpf/verifier.c:17016
 do_check_insn kernel/bpf/verifier.c:20441 [inline]
 do_check+0x23ef/0x16a50 kernel/bpf/verifier.c:20581
 do_check_common+0x2217/0x3370 kernel/bpf/verifier.c:23865
 do_check_main kernel/bpf/verifier.c:23948 [inline]
 bpf_check+0x1e78c/0x27610 kernel/bpf/verifier.c:25255
 bpf_prog_load+0x2af6/0x3100 kernel/bpf/syscall.c:3088
 __sys_bpf+0x7df/0xeb0 kernel/bpf/syscall.c:6164
 __do_sys_bpf kernel/bpf/syscall.c:6274 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6272 [inline]
 __x64_sys_bpf+0xa4/0xf0 kernel/bpf/syscall.c:6272
 x64_sys_call+0x31c3/0x3e70 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was stored to memory at:
 vsnprintf+0x15d2/0x1b30 lib/vsprintf.c:-1
 vprintk_store+0x3ae/0x1530 kernel/printk/printk.c:2255
 vprintk_emit+0x27b/0xc50 kernel/printk/printk.c:2402
 vprintk_default+0x3f/0x50 kernel/printk/printk.c:2441
 vprintk+0x36/0x50 kernel/printk/printk_safe.c:82
 __warn_printf lib/bug.c:187 [inline]
 __report_bug+0xa53/0xe80 lib/bug.c:240
 report_bug_entry+0x148/0x1d0 lib/bug.c:265
 handle_bug+0xe1/0x230 arch/x86/kernel/traps.c:430
 exc_invalid_op+0x1f/0x50 arch/x86/kernel/traps.c:489
 asm_exc_invalid_op+0x1f/0x30 arch/x86/include/asm/idtentry.h:616

Local variable run_ctx.i created at:
 __bpf_trace_run kernel/trace/bpf_trace.c:2063 [inline]
 bpf_trace_run4+0xdf/0x590 kernel/trace/bpf_trace.c:2118
 __bpf_trace_sched_switch+0x221/0x290 include/trace/events/sched.h:220

CPU: 1 UID: 0 PID: 23594 Comm: syz.7.5009 Tainted: G        W           syzkaller #0 PREEMPT(none) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
=====================================================


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Re: [syzbot] [bpf?] KMSAN: uninit-value in handle_bug

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    2d1373e4246d Merge tag 'for-7.0-rc4-tag' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=146bc4da580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=963de479f54c6dbb
dashboard link: https://syzkaller.appspot.com/bug?extid=ba80855313e6fa65717a
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14b4a8da580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16773406580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bef78207d3f7/disk-2d1373e4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/35fd28ca5034/vmlinux-2d1373e4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c2b759faae9e/bzImage-2d1373e4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ba80855313e6fa65717a@syzkaller.appspotmail.com

------------[ cut here ]------------
=====================================================
BUG: KMSAN: uninit-value in vsnprintf+0x15be/0x1b00 lib/vsprintf.c:2912
 vsnprintf+0x15be/0x1b00 lib/vsprintf.c:2912
 vprintk_store+0x350/0x1550 kernel/printk/printk.c:2307
 vprintk_emit+0x2c8/0xba0 kernel/printk/printk.c:2455
 vprintk_default+0x3f/0x50 kernel/printk/printk.c:2494
 vprintk+0x36/0x50 kernel/printk/printk_safe.c:82
 __warn_printf lib/bug.c:190 [inline]
 __report_bug+0xa10/0xe00 lib/bug.c:244
 report_bug_entry+0x17c/0x220 lib/bug.c:269
 handle_bug+0xe5/0x230 arch/x86/kernel/traps.c:430
 exc_invalid_op+0x1f/0x50 arch/x86/kernel/traps.c:489
 asm_exc_invalid_op+0x1f/0x30 arch/x86/include/asm/idtentry.h:616
 reg_bounds_sanity_check+0x571/0x14e0 kernel/bpf/verifier.c:2817
 reg_set_min_max+0x34b/0x450 kernel/bpf/verifier.c:17159
 check_cond_jmp_op+0x3bf5/0x5370 kernel/bpf/verifier.c:17609
 do_check_insn kernel/bpf/verifier.c:21168 [inline]
 do_check+0xc7e8/0x1add0 kernel/bpf/verifier.c:21308
 do_check_common+0x2705/0x4270 kernel/bpf/verifier.c:24650
 do_check_main kernel/bpf/verifier.c:24733 [inline]
 bpf_check+0x1f159/0x27e90 kernel/bpf/verifier.c:26056
 bpf_prog_load+0x2b41/0x3140 kernel/bpf/syscall.c:3089
 __sys_bpf+0x8e0/0xee0 kernel/bpf/syscall.c:6228
 __do_sys_bpf kernel/bpf/syscall.c:6341 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6339 [inline]
 __x64_sys_bpf+0xa4/0xf0 kernel/bpf/syscall.c:6339
 x64_sys_call+0x13d0/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was stored to memory at:
 vsnprintf+0x15b7/0x1b00 lib/vsprintf.c:-1
 vprintk_store+0x350/0x1550 kernel/printk/printk.c:2307
 vprintk_emit+0x2c8/0xba0 kernel/printk/printk.c:2455
 vprintk_default+0x3f/0x50 kernel/printk/printk.c:2494
 vprintk+0x36/0x50 kernel/printk/printk_safe.c:82
 __warn_printf lib/bug.c:190 [inline]
 __report_bug+0xa10/0xe00 lib/bug.c:244
 report_bug_entry+0x17c/0x220 lib/bug.c:269
 handle_bug+0xe5/0x230 arch/x86/kernel/traps.c:430
 exc_invalid_op+0x1f/0x50 arch/x86/kernel/traps.c:489
 asm_exc_invalid_op+0x1f/0x30 arch/x86/include/asm/idtentry.h:616

Local variable pflags created at:
 try_charge_memcg+0x63/0x1c20 mm/memcontrol.c:2367
 obj_cgroup_charge_pages+0x69/0x330 mm/memcontrol.c:2857

CPU: 1 UID: 0 PID: 5997 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
=====================================================


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