On Thu, Nov 8, 2018 at 9:38 PM syzbot <syzbot+1cb36954e127c98dd037@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > syzbot found the following crash on: > > HEAD commit: 7438a3b20295 kmsan: print user address when reporting info.. > git tree: https://github.com/google/kmsan.git/master > console output: https://syzkaller.appspot.com/x/log.txt?x=15b42133400000 > kernel config: https://syzkaller.appspot.com/x/.config?x=8df5fc509a1b351b > dashboard link: https://syzkaller.appspot.com/bug?extid=1cb36954e127c98dd037 > compiler: clang version 8.0.0 (trunk 343298) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12be9825400000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13e2c425400000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+1cb36954e127c98dd037@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================================================== > BUG: KMSAN: uninit-value in __arch_swab32 > arch/x86/include/uapi/asm/swab.h:10 [inline] > BUG: KMSAN: uninit-value in __fswab32 include/uapi/linux/swab.h:59 [inline] > BUG: KMSAN: uninit-value in do_convert sound/core/oss/linear.c:50 [inline] > BUG: KMSAN: uninit-value in convert sound/core/oss/linear.c:81 [inline] > BUG: KMSAN: uninit-value in linear_transfer+0x92d/0xca0 > sound/core/oss/linear.c:110 > CPU: 1 PID: 6835 Comm: syz-executor866 Not tainted 4.19.0+ #78 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x32d/0x480 lib/dump_stack.c:113 > kmsan_report+0x19f/0x300 mm/kmsan/kmsan.c:911 > __msan_warning+0x76/0xd0 mm/kmsan/kmsan_instr.c:415 > __arch_swab32 arch/x86/include/uapi/asm/swab.h:10 [inline] > __fswab32 include/uapi/linux/swab.h:59 [inline] > do_convert sound/core/oss/linear.c:50 [inline] > convert sound/core/oss/linear.c:81 [inline] > linear_transfer+0x92d/0xca0 sound/core/oss/linear.c:110 > snd_pcm_plug_read_transfer+0x3bf/0x590 sound/core/oss/pcm_plugin.c:659 > snd_pcm_oss_read2 sound/core/oss/pcm_oss.c:1480 [inline] > snd_pcm_oss_read1 sound/core/oss/pcm_oss.c:1518 [inline] > snd_pcm_oss_read+0xe6d/0x1cb0 sound/core/oss/pcm_oss.c:2758 > __vfs_read+0x1e2/0xb10 fs/read_write.c:416 > vfs_read+0x380/0x6b0 fs/read_write.c:452 > ksys_read fs/read_write.c:578 [inline] > __do_sys_read fs/read_write.c:588 [inline] > __se_sys_read+0x17a/0x370 fs/read_write.c:586 > __x64_sys_read+0x4a/0x70 fs/read_write.c:586 > do_syscall_64+0xcf/0x110 arch/x86/entry/common.c:291 > entry_SYSCALL_64_after_hwframe+0x63/0xe7 > RIP: 0033:0x446379 > Code: e8 0c e8 ff ff 48 83 c4 18 c3 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 0f 83 7b 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007fcd5b97cda8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 > RAX: ffffffffffffffda RBX: 00000000006dac38 RCX: 0000000000446379 > RDX: 0000000000000184 RSI: 0000000020002180 RDI: 0000000000000003 > RBP: 00000000006dac30 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac3c > R13: 7073642f7665642f R14: 00800000c0045002 R15: 0000000000000001 > > Uninit was stored to memory at: > kmsan_save_stack_with_flags mm/kmsan/kmsan.c:252 [inline] > kmsan_save_stack mm/kmsan/kmsan.c:267 [inline] > kmsan_internal_chain_origin+0x136/0x240 mm/kmsan/kmsan.c:569 > kmsan_memcpy_origins+0x13d/0x1b0 mm/kmsan/kmsan.c:393 > __msan_memcpy+0x6f/0x80 mm/kmsan/kmsan_instr.c:242 > do_convert sound/core/oss/linear.c:48 [inline] > convert sound/core/oss/linear.c:81 [inline] > linear_transfer+0x74c/0xca0 sound/core/oss/linear.c:110 > snd_pcm_plug_read_transfer+0x3bf/0x590 sound/core/oss/pcm_plugin.c:659 > snd_pcm_oss_read2 sound/core/oss/pcm_oss.c:1480 [inline] > snd_pcm_oss_read1 sound/core/oss/pcm_oss.c:1518 [inline] > snd_pcm_oss_read+0xe6d/0x1cb0 sound/core/oss/pcm_oss.c:2758 > __vfs_read+0x1e2/0xb10 fs/read_write.c:416 > vfs_read+0x380/0x6b0 fs/read_write.c:452 > ksys_read fs/read_write.c:578 [inline] > __do_sys_read fs/read_write.c:588 [inline] > __se_sys_read+0x17a/0x370 fs/read_write.c:586 > __x64_sys_read+0x4a/0x70 fs/read_write.c:586 > do_syscall_64+0xcf/0x110 arch/x86/entry/common.c:291 > entry_SYSCALL_64_after_hwframe+0x63/0xe7 > > Uninit was created at: > kmsan_save_stack_with_flags mm/kmsan/kmsan.c:252 [inline] > kmsan_internal_alloc_meta_for_pages+0x155/0x740 mm/kmsan/kmsan.c:689 > kmsan_alloc_page+0x77/0xe0 mm/kmsan/kmsan_hooks.c:320 > __alloc_pages_nodemask+0x12cc/0x6640 mm/page_alloc.c:4416 > alloc_pages_current+0x584/0x7e0 mm/mempolicy.c:2093 > alloc_pages include/linux/gfp.h:511 [inline] > __vmalloc_area_node mm/vmalloc.c:1689 [inline] > __vmalloc_node_range+0x879/0x12a0 mm/vmalloc.c:1752 > __vmalloc_node mm/vmalloc.c:1797 [inline] > __vmalloc_node_flags mm/vmalloc.c:1811 [inline] > vmalloc+0xd8/0xf0 mm/vmalloc.c:1833 > snd_pcm_plugin_alloc+0x255/0xc80 sound/core/oss/pcm_plugin.c:71 > snd_pcm_plug_alloc+0x281/0x600 sound/core/oss/pcm_plugin.c:137 > snd_pcm_oss_change_params_locked+0x5e40/0x6e30 > sound/core/oss/pcm_oss.c:1039 > snd_pcm_oss_change_params sound/core/oss/pcm_oss.c:1107 [inline] > snd_pcm_oss_get_active_substream+0x4f7/0x5a0 sound/core/oss/pcm_oss.c:1124 > snd_pcm_oss_get_rate sound/core/oss/pcm_oss.c:1774 [inline] > snd_pcm_oss_set_rate sound/core/oss/pcm_oss.c:1766 [inline] > snd_pcm_oss_ioctl+0x4adb/0x8860 sound/core/oss/pcm_oss.c:2614 > do_vfs_ioctl+0xf77/0x2d30 fs/ioctl.c:46 > ksys_ioctl fs/ioctl.c:702 [inline] > __do_sys_ioctl fs/ioctl.c:709 [inline] > __se_sys_ioctl+0x1da/0x270 fs/ioctl.c:707 > __x64_sys_ioctl+0x4a/0x70 fs/ioctl.c:707 > do_syscall_64+0xcf/0x110 arch/x86/entry/common.c:291 > entry_SYSCALL_64_after_hwframe+0x63/0xe7 > ================================================================== I am actually unsure whether this is a true positive or not. snd_pcm_plugin_alloc() allocates plugin->buf using vmalloc(size) (see https://elixir.bootlin.com/linux/v4.20-rc1/source/sound/core/oss/pcm_plugin.c#L70) KMSAN doesn't know where this buffer is initialized (any help finding this out is welcome!), so we mark |size| bytes starting from plugin->buf as initialized: https://github.com/google/kmsan/blob/master/sound/core/oss/pcm_plugin.c#L78 But when |size| is not page-aligned vmalloc() still allocates whole page, and in the report above linear_transfer() appears to run past |size| bytes and read the tail bytes. KASAN doesn't detect this bug, because it doesn't handle vmalloc'ed (and these bytes are addressable anyway). The reproducer that triggers this bug is attached. > > --- > This bug 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 bug report. See: > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with > syzbot. > syzbot can test patches for this bug, for details see: > https://goo.gl/tpsmEJ#testing-patches > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/00000000000021d9a9057a2d364e%40google.com. > For more options, visit https://groups.google.com/d/optout. -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
// autogenerated by syzkaller (https://github.com/google/syzkaller) #define _GNU_SOURCE #include <stdint.h> #include <unistd.h> #include <sys/ioctl.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> uint64_t fd = -1; #define BUF_SIZE 0x18 static void execute_one() { long res; char buf[BUF_SIZE]; res = openat(AT_FDCWD, "/dev/dsp", 0xe02, 0); if (res != -1) fd = res; uint64_t arg = 0x10000; ioctl(fd, 0x800000c0045002, &arg); usleep(100000); read(fd, buf, BUF_SIZE); } int main(void) { int procid; for (procid = 0; procid < 4; procid++) { if (fork() == 0) { execute_one(); } } sleep(1000000); return 0; }
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