Hello,

syzbot found the following issue on:

HEAD commit: 8fe31e0995f0 Merge tag 'gpio-fixes-for-v5.15-rc6' of git:/.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=16a58d94b00000 kernel config: https://syzkaller.appspot.com/x/.config?x=bab9d35f204746a7 dashboard link: https://syzkaller.appspot.com/bug?extid=9988f17cf72a1045a189 compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 userspace arch: i386 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10251d58b00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17039278b00000

Bisection is inconclusive: the issue happens on the oldest tested release.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=167855f4b00000 final oops: https://syzkaller.appspot.com/x/report.txt?x=157855f4b00000 console output: https://syzkaller.appspot.com/x/log.txt?x=117855f4b00000

IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+9988f17cf72a1045a189@syzkaller.appspotmail.com

================================================================== BUG: KASAN: use-after-free in snd_mixer_oss_get_volume1+0x574/0x610 sound/core/oss/mixer_oss.c:600 Read of size 4 at addr ffff888070afc984 by task syz-executor166/6533

CPU: 0 PID: 6533 Comm: syz-executor166 Not tainted 5.15.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:256 __kasan_report mm/kasan/report.c:442 [inline] kasan_report.cold+0x83/0xdf mm/kasan/report.c:459 snd_mixer_oss_get_volume1+0x574/0x610 sound/core/oss/mixer_oss.c:600 snd_mixer_oss_get_volume sound/core/oss/mixer_oss.c:258 [inline] snd_mixer_oss_ioctl1+0x249/0x1880 sound/core/oss/mixer_oss.c:358 snd_mixer_oss_ioctl_compat+0x45/0x60 sound/core/oss/mixer_oss.c:391 __do_compat_sys_ioctl+0x1c7/0x290 fs/ioctl.c:972 do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline] __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c RIP: 0023:0xf7f42549 Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00 RSP: 002b:00000000ffa708bc EFLAGS: 00000246 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000080254d18 RDX: 0000000000000000 RSI: 0000000003700000 RDI: 0000000001000000 RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6526: kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38 kasan_set_track mm/kasan/common.c:46 [inline] set_alloc_info mm/kasan/common.c:434 [inline] ____kasan_kmalloc mm/kasan/common.c:513 [inline] ____kasan_kmalloc mm/kasan/common.c:472 [inline] __kasan_kmalloc+0xa4/0xd0 mm/kasan/common.c:522 kmalloc include/linux/slab.h:591 [inline] snd_mixer_oss_build_input+0x656/0xe30 sound/core/oss/mixer_oss.c:1093 snd_mixer_oss_proc_write+0x384/0x5c0 sound/core/oss/mixer_oss.c:1233 snd_info_text_entry_release+0xfa/0x260 sound/core/info.c:408 close_pdeo.part.0+0xdc/0x2e0 fs/proc/inode.c:244 close_pdeo fs/proc/inode.c:563 [inline] proc_reg_release+0x2e9/0x360 fs/proc/inode.c:562 __fput+0x288/0x9f0 fs/file_table.c:280 task_work_run+0xdd/0x1a0 kernel/task_work.c:164 exit_task_work include/linux/task_work.h:32 [inline] do_exit+0xbae/0x2a30 kernel/exit.c:825 do_group_exit+0x125/0x310 kernel/exit.c:922 __do_sys_exit_group kernel/exit.c:933 [inline] __se_sys_exit_group kernel/exit.c:931 [inline] __ia32_sys_exit_group+0x3a/0x50 kernel/exit.c:931 do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline] __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

Freed by task 6531: kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38 kasan_set_track+0x1c/0x30 mm/kasan/common.c:46 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:360 ____kasan_slab_free mm/kasan/common.c:366 [inline] ____kasan_slab_free mm/kasan/common.c:328 [inline] __kasan_slab_free+0xff/0x130 mm/kasan/common.c:374 kasan_slab_free include/linux/kasan.h:230 [inline] slab_free_hook mm/slub.c:1700 [inline] slab_free_freelist_hook+0x81/0x190 mm/slub.c:1725 slab_free mm/slub.c:3483 [inline] kfree+0xe4/0x530 mm/slub.c:4543 snd_mixer_oss_slot_free+0xf3/0x130 sound/core/oss/mixer_oss.c:951 mixer_slot_clear+0x5a/0xb0 sound/core/oss/mixer_oss.c:959 snd_mixer_oss_build_input+0x7f0/0xe30 sound/core/oss/mixer_oss.c:1101 snd_mixer_oss_proc_write+0x384/0x5c0 sound/core/oss/mixer_oss.c:1233 snd_info_text_entry_release+0xfa/0x260 sound/core/info.c:408 close_pdeo.part.0+0xdc/0x2e0 fs/proc/inode.c:244 close_pdeo fs/proc/inode.c:563 [inline] proc_reg_release+0x2e9/0x360 fs/proc/inode.c:562 __fput+0x288/0x9f0 fs/file_table.c:280 task_work_run+0xdd/0x1a0 kernel/task_work.c:164 exit_task_work include/linux/task_work.h:32 [inline] do_exit+0xbae/0x2a30 kernel/exit.c:825 do_group_exit+0x125/0x310 kernel/exit.c:922 __do_sys_exit_group kernel/exit.c:933 [inline] __se_sys_exit_group kernel/exit.c:931 [inline] __ia32_sys_exit_group+0x3a/0x50 kernel/exit.c:931 do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline] __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

The buggy address belongs to the object at ffff888070afc980 which belongs to the cache kmalloc-96 of size 96 The buggy address is located 4 bytes inside of 96-byte region [ffff888070afc980, ffff888070afc9e0) The buggy address belongs to the page: page:ffffea0001c2bf00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x70afc flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000000200 ffffea0000725740 0000000700000007 ffff888010c41780 raw: 0000000000000000 0000000000200020 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY), pid 4486, ts 39889903663, free_ts 39887746705 prep_new_page mm/page_alloc.c:2424 [inline] get_page_from_freelist+0xa72/0x2f80 mm/page_alloc.c:4153 __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5375 alloc_pages+0x1a7/0x300 mm/mempolicy.c:2197 alloc_slab_page mm/slub.c:1763 [inline] allocate_slab mm/slub.c:1900 [inline] new_slab+0x319/0x490 mm/slub.c:1963 ___slab_alloc+0x921/0xfe0 mm/slub.c:2994 __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3081 slab_alloc_node mm/slub.c:3172 [inline] slab_alloc mm/slub.c:3214 [inline] __kmalloc+0x305/0x320 mm/slub.c:4387 kmalloc include/linux/slab.h:596 [inline] kzalloc include/linux/slab.h:721 [inline] tomoyo_encode2.part.0+0xe9/0x3a0 security/tomoyo/realpath.c:45 tomoyo_encode2 security/tomoyo/realpath.c:31 [inline] tomoyo_encode+0x28/0x50 security/tomoyo/realpath.c:80 tomoyo_realpath_from_path+0x186/0x620 security/tomoyo/realpath.c:288 tomoyo_get_realpath security/tomoyo/file.c:151 [inline] tomoyo_check_open_permission+0x272/0x380 security/tomoyo/file.c:771 tomoyo_file_open security/tomoyo/tomoyo.c:311 [inline] tomoyo_file_open+0xa3/0xd0 security/tomoyo/tomoyo.c:306 security_file_open+0x45/0xb0 security/security.c:1634 do_dentry_open+0x353/0x11d0 fs/open.c:809 do_open fs/namei.c:3428 [inline] path_openat+0x1c9a/0x2740 fs/namei.c:3561 do_filp_open+0x1aa/0x400 fs/namei.c:3588 page last free stack trace: reset_page_owner include/linux/page_owner.h:24 [inline] free_pages_prepare mm/page_alloc.c:1338 [inline] free_pcp_prepare+0x2c5/0x780 mm/page_alloc.c:1389 free_unref_page_prepare mm/page_alloc.c:3315 [inline] free_unref_page+0x19/0x690 mm/page_alloc.c:3394 __vunmap+0x783/0xb70 mm/vmalloc.c:2621 free_work+0x58/0x70 mm/vmalloc.c:95 process_one_work+0x9bf/0x16b0 kernel/workqueue.c:2297 worker_thread+0x658/0x11f0 kernel/workqueue.c:2444 kthread+0x3e5/0x4d0 kernel/kthread.c:319 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Memory state around the buggy address: ffff888070afc880: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc ffff888070afc900: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc

ffff888070afc980: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc

^ ffff888070afca00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ffff888070afca80: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ================================================================== ---------------- Code disassembly (best guess): 0: 03 74 c0 01 add 0x1(%rax,%rax,8),%esi 4: 10 05 03 74 b8 01 adc %al,0x1b87403(%rip) # 0x1b8740d a: 10 06 adc %al,(%rsi) c: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi 10: 10 07 adc %al,(%rdi) 12: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi 16: 10 08 adc %cl,(%rax) 18: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi 1c: 00 00 add %al,(%rax) 1e: 00 00 add %al,(%rax) 20: 00 51 52 add %dl,0x52(%rcx) 23: 55 push %rbp 24: 89 e5 mov %esp,%ebp 26: 0f 34 sysenter 28: cd 80 int $0x80 * 2a: 5d pop %rbp <-- trapping instruction 2b: 5a pop %rdx 2c: 59 pop %rcx 2d: c3 retq 2e: 90 nop 2f: 90 nop 30: 90 nop 31: 90 nop 32: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi 39: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi

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