bisecting cause commit starting from 311ef88adfa3b69c40234bf3000d1269e718919a
building syzkaller on b2f369e56e13dc135d57c53210ea7ab38b239e94
testing commit 311ef88adfa3b69c40234bf3000d1269e718919a with gcc (GCC) 8.1.0
run #0: crashed: KASAN: use-after-free Read in do_mount
run #1: crashed: KASAN: use-after-free Read in do_mount
run #2: crashed: KASAN: use-after-free Read in do_mount
run #3: crashed: KASAN: use-after-free Read in do_mount
run #4: crashed: KASAN: use-after-free Read in do_mount
run #5: crashed: KASAN: use-after-free Read in do_mount
run #6: crashed: KASAN: use-after-free Read in do_mount
run #7: crashed: KASAN: use-after-free Read in do_mount
run #8: OK
run #9: OK
testing release v5.3
testing commit 4d856f72c10ecb060868ed10ff1b1453943fc6c8 with gcc (GCC) 8.1.0
all runs: OK
# git bisect start 311ef88adfa3b69c40234bf3000d1269e718919a v5.3
Bisecting: 7878 revisions left to test after this (roughly 13 steps)
[a9f8b38a071b468276a243ea3ea5a0636e848cf2] Merge tag 'for-linus-5.4-1' of git://github.com/cminyard/linux-ipmi
testing commit a9f8b38a071b468276a243ea3ea5a0636e848cf2 with gcc (GCC) 8.1.0
run #0: crashed: KASAN: use-after-free Read in do_mount
run #1: crashed: KASAN: use-after-free Read in do_mount
run #2: crashed: KASAN: use-after-free Read in do_mount
run #3: crashed: KASAN: use-after-free Read in do_mount
run #4: crashed: KASAN: use-after-free Read in do_mount
run #5: crashed: KASAN: use-after-free Read in do_mount
run #6: crashed: KASAN: use-after-free Read in do_mount
run #7: crashed: KASAN: use-after-free Read in do_mount
run #8: crashed: KASAN: use-after-free Read in do_mount
run #9: OK
# git bisect bad a9f8b38a071b468276a243ea3ea5a0636e848cf2
Bisecting: 3920 revisions left to test after this (roughly 12 steps)
[fe38bd6862074c0a2b9be7f31f043aaa70b2af5f] Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
testing commit fe38bd6862074c0a2b9be7f31f043aaa70b2af5f with gcc (GCC) 8.1.0
all runs: OK
# git bisect good fe38bd6862074c0a2b9be7f31f043aaa70b2af5f
Bisecting: 1962 revisions left to test after this (roughly 11 steps)
[069841ef8293697e951c34f9a45601b77fb541d7] Merge branch '40GbE' of git://git.kernel.org/pub/scm/linux/kernel/git/jkirsher/next-queue
testing commit 069841ef8293697e951c34f9a45601b77fb541d7 with gcc (GCC) 8.1.0
all runs: OK
# git bisect good 069841ef8293697e951c34f9a45601b77fb541d7
Bisecting: 939 revisions left to test after this (roughly 10 steps)
[6cfae0c26b21dce323fe8799b66cf4bc996e3565] Merge tag 'char-misc-5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc
testing commit 6cfae0c26b21dce323fe8799b66cf4bc996e3565 with gcc (GCC) 8.1.0
all runs: OK
# git bisect good 6cfae0c26b21dce323fe8799b66cf4bc996e3565
Bisecting: 471 revisions left to test after this (roughly 9 steps)
[81160dda9a7aad13c04e78bb2cfd3c4630e3afab] Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next
testing commit 81160dda9a7aad13c04e78bb2cfd3c4630e3afab with gcc (GCC) 8.1.0
all runs: OK
# git bisect good 81160dda9a7aad13c04e78bb2cfd3c4630e3afab
Bisecting: 248 revisions left to test after this (roughly 8 steps)
[e6bc9de714972cac34daa1dc1567ee48a47a9342] Merge tag 'vfs-5.4-merge-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux
testing commit e6bc9de714972cac34daa1dc1567ee48a47a9342 with gcc (GCC) 8.1.0
all runs: OK
# git bisect good e6bc9de714972cac34daa1dc1567ee48a47a9342
Bisecting: 119 revisions left to test after this (roughly 7 steps)
[7e3d2c8210e67ebff472a0b371bb0efb4236ef52] Merge tag '5.4-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6
testing commit 7e3d2c8210e67ebff472a0b371bb0efb4236ef52 with gcc (GCC) 8.1.0
run #0: crashed: KASAN: use-after-free Read in do_mount
run #1: crashed: KASAN: use-after-free Read in do_mount
run #2: crashed: KASAN: use-after-free Read in do_mount
run #3: crashed: KASAN: use-after-free Read in do_mount
run #4: crashed: KASAN: use-after-free Read in do_mount
run #5: crashed: KASAN: use-after-free Read in do_mount
run #6: crashed: KASAN: use-after-free Read in do_mount
run #7: crashed: KASAN: use-after-free Read in do_mount
run #8: crashed: KASAN: use-after-free Read in do_mount
run #9: OK
# git bisect bad 7e3d2c8210e67ebff472a0b371bb0efb4236ef52
Bisecting: 61 revisions left to test after this (roughly 6 steps)
[cfb82e1df8b7c76991ea12958855897c2fb4debc] Merge tag 'y2038-vfs' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground
testing commit cfb82e1df8b7c76991ea12958855897c2fb4debc with gcc (GCC) 8.1.0
run #0: crashed: KASAN: use-after-free Read in do_mount
run #1: crashed: KASAN: use-after-free Read in do_mount
run #2: crashed: KASAN: use-after-free Read in do_mount
run #3: crashed: KASAN: use-after-free Read in do_mount
run #4: crashed: KASAN: use-after-free Read in do_mount
run #5: crashed: KASAN: use-after-free Read in do_mount
run #6: crashed: KASAN: use-after-free Read in do_mount
run #7: OK
run #8: OK
run #9: OK
# git bisect bad cfb82e1df8b7c76991ea12958855897c2fb4debc
Bisecting: 33 revisions left to test after this (roughly 5 steps)
[1baa2800e62d7d58c04cb871a6e4189fc3e1ccf1] xfs: remove the unused XFS_ALLOC_USERDATA flag
testing commit 1baa2800e62d7d58c04cb871a6e4189fc3e1ccf1 with gcc (GCC) 8.1.0
all runs: OK
# git bisect good 1baa2800e62d7d58c04cb871a6e4189fc3e1ccf1
Bisecting: 16 revisions left to test after this (roughly 4 steps)
[83b8a3fbe3aa82ac3c253b698ae6a9be2dbdd5e0] pstore: fs superblock limits
testing commit 83b8a3fbe3aa82ac3c253b698ae6a9be2dbdd5e0 with gcc (GCC) 8.1.0
all runs: OK
# git bisect good 83b8a3fbe3aa82ac3c253b698ae6a9be2dbdd5e0
Bisecting: 8 revisions left to test after this (roughly 3 steps)
[6769aa2a4f2b02ec9952091ad8c853056a7c7b9c] xfs: factor debug code out of xlog_state_do_callback()
testing commit 6769aa2a4f2b02ec9952091ad8c853056a7c7b9c with gcc (GCC) 8.1.0
all runs: OK
# git bisect good 6769aa2a4f2b02ec9952091ad8c853056a7c7b9c
Bisecting: 4 revisions left to test after this (roughly 2 steps)
[14e15f1bcd738dc13dd7c1e78e4800e8bc577980] xfs: push the grant head when the log head moves forward
testing commit 14e15f1bcd738dc13dd7c1e78e4800e8bc577980 with gcc (GCC) 8.1.0
all runs: OK
# git bisect good 14e15f1bcd738dc13dd7c1e78e4800e8bc577980
Bisecting: 2 revisions left to test after this (roughly 1 step)
[9d14545b05f9eed69fbd4af14b927a462324ea19] Merge branch 'limits' of https://github.com/deepa-hub/vfs into y2038
testing commit 9d14545b05f9eed69fbd4af14b927a462324ea19 with gcc (GCC) 8.1.0
run #0: crashed: KASAN: use-after-free Read in do_mount
run #1: OK
run #2: OK
run #3: OK
run #4: OK
run #5: OK
run #6: OK
run #7: OK
run #8: OK
run #9: OK
# git bisect bad 9d14545b05f9eed69fbd4af14b927a462324ea19
Bisecting: 0 revisions left to test after this (roughly 0 steps)
[5ad32b3acded06183f40806f76b030c3143017bb] isofs: Initialize filesystem timestamp ranges
testing commit 5ad32b3acded06183f40806f76b030c3143017bb with gcc (GCC) 8.1.0
all runs: OK
# git bisect good 5ad32b3acded06183f40806f76b030c3143017bb
9d14545b05f9eed69fbd4af14b927a462324ea19 is the first bad commit
revisions tested: 16, total time: 4h24m10.631748836s (build: 1h36m26.769610008s, test: 2h42m19.132531068s)
first bad commit: 9d14545b05f9eed69fbd4af14b927a462324ea19 Merge branch 'limits' of https://github.com/deepa-hub/vfs into y2038
cc: ["anton@enomsg.org" "arnd@arndb.de" "ccross@android.com" "keescook@chromium.org" "tony.luck@intel.com"]
crash: KASAN: use-after-free Read in do_mount
==================================================================
BUG: KASAN: use-after-free in do_new_mount_fc fs/namespace.c:2770 [inline]
BUG: KASAN: use-after-free in do_new_mount fs/namespace.c:2824 [inline]
BUG: KASAN: use-after-free in do_mount+0x19a7/0x1bd0 fs/namespace.c:3142
Read of size 8 at addr ffff88808ba7b968 by task syz-executor.4/4471

CPU: 0 PID: 4471 Comm: syz-executor.4 Not tainted 5.3.0-rc6+ #0
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+0x113/0x167 lib/dump_stack.c:113
 print_address_description.cold.8+0x9/0x318 mm/kasan/report.c:351
 __kasan_report.cold.9+0x1b/0x3f mm/kasan/report.c:482
 kasan_report+0x12/0x17 mm/kasan/common.c:618
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
 do_new_mount_fc fs/namespace.c:2770 [inline]
 do_new_mount fs/namespace.c:2824 [inline]
 do_mount+0x19a7/0x1bd0 fs/namespace.c:3142
 ksys_mount+0xba/0xe0 fs/namespace.c:3351
 __do_sys_mount fs/namespace.c:3365 [inline]
 __se_sys_mount fs/namespace.c:3362 [inline]
 __x64_sys_mount+0xb9/0x150 fs/namespace.c:3362
 do_syscall_64+0xd0/0x540 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459a59
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f6fe32d6c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000459a59
RDX: 0000000020000a40 RSI: 00000000200005c0 RDI: 0000000000000000
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6fe32d76d4
R13: 00000000004c6291 R14: 00000000004db2f8 R15: 00000000ffffffff

Allocated by task 4471:
 save_stack+0x21/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_kmalloc.constprop.9+0xc7/0xd0 mm/kasan/common.c:493
 kasan_slab_alloc+0x12/0x20 mm/kasan/common.c:501
 slab_post_alloc_hook mm/slab.h:520 [inline]
 slab_alloc mm/slab.c:3319 [inline]
 kmem_cache_alloc+0x121/0x750 mm/slab.c:3483
 kmem_cache_zalloc include/linux/slab.h:738 [inline]
 alloc_vfsmnt+0x21/0x620 fs/namespace.c:177
 vfs_create_mount+0x8a/0x4b0 fs/namespace.c:940
 do_new_mount_fc fs/namespace.c:2760 [inline]
 do_new_mount fs/namespace.c:2824 [inline]
 do_mount+0x14c1/0x1bd0 fs/namespace.c:3142
 ksys_mount+0xba/0xe0 fs/namespace.c:3351
 __do_sys_mount fs/namespace.c:3365 [inline]
 __se_sys_mount fs/namespace.c:3362 [inline]
 __x64_sys_mount+0xb9/0x150 fs/namespace.c:3362
 do_syscall_64+0xd0/0x540 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4481:
 save_stack+0x21/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:455
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:463
 __cache_free mm/slab.c:3425 [inline]
 kmem_cache_free+0x83/0x320 mm/slab.c:3693
 free_vfsmnt+0x62/0x80 fs/namespace.c:554
 delayed_free_vfsmnt+0xd/0x10 fs/namespace.c:559
 __rcu_reclaim kernel/rcu/rcu.h:222 [inline]
 rcu_do_batch kernel/rcu/tree.c:2114 [inline]
 rcu_core+0x65e/0x14c0 kernel/rcu/tree.c:2314
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2323
 __do_softirq+0x262/0x9a8 kernel/softirq.c:292

The buggy address belongs to the object at ffff88808ba7b940
 which belongs to the cache mnt_cache of size 312
The buggy address is located 40 bytes inside of
 312-byte region [ffff88808ba7b940, ffff88808ba7ba78)
The buggy address belongs to the page:
page:ffffea00022e9ec0 refcount:1 mapcount:0 mapping:ffff8880aa593a80 index:0xffff88808ba7bdc0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea000265f388 ffffea00028674c8 ffff8880aa593a80
raw: ffff88808ba7bdc0 ffff88808ba7b040 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808ba7b800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808ba7b880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
>ffff88808ba7b900: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                          ^
 ffff88808ba7b980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808ba7ba00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
==================================================================