bisecting fixing commit since 549738f15da0e5a00275977623be199fbbf7df50
building syzkaller on 5ef9c29141f85f210b326ce68718498ae0c1fd35
testing commit 549738f15da0e5a00275977623be199fbbf7df50 with gcc (GCC) 8.4.1 20210217
kernel signature: 7302d9c395f3d39d61a7e7aeb4e0e62816567f3af4fb1340f9cede9e1ced5cf0
all runs: crashed: KASAN: slab-out-of-bounds Read in qrtr_endpoint_post
testing current HEAD 8b12a62a4e3ed4ae99c715034f557eb391d6b196
testing commit 8b12a62a4e3ed4ae99c715034f557eb391d6b196 with gcc (GCC) 10.2.1 20210217
kernel signature: b4edeaa34539136662aad9f07319e3183e31158a6d4d1f131f11aa5449a1cb79
all runs: crashed: KASAN: slab-out-of-bounds Read in qrtr_endpoint_post
revisions tested: 2, total time: 20m42.820781014s (build: 13m20.391373031s, test: 6m35.573065825s)
the crash still happens on HEAD
commit msg: Merge tag 'drm-fixes-2021-03-19' of git://anongit.freedesktop.org/drm/drm
crash: KASAN: slab-out-of-bounds Read in qrtr_endpoint_post
==================================================================
BUG: KASAN: slab-out-of-bounds in memcpy include/linux/fortify-string.h:191 [inline]
BUG: KASAN: slab-out-of-bounds in skb_put_data include/linux/skbuff.h:2293 [inline]
BUG: KASAN: slab-out-of-bounds in qrtr_endpoint_post+0x4f1/0x1070 net/qrtr/qrtr.c:499
Read of size 4294967293 at addr ffff888102133d60 by task syz-executor.2/7534

CPU: 0 PID: 7534 Comm: syz-executor.2 Not tainted 5.12.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x10c/0x14b lib/dump_stack.c:120
 print_address_description.constprop.0.cold+0x5b/0x2c6 mm/kasan/report.c:232
 __kasan_report mm/kasan/report.c:399 [inline]
 kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:416
 check_region_inline mm/kasan/generic.c:180 [inline]
 kasan_check_range+0x13d/0x180 mm/kasan/generic.c:186
 memcpy+0x20/0x60 mm/kasan/shadow.c:65
 memcpy include/linux/fortify-string.h:191 [inline]
 skb_put_data include/linux/skbuff.h:2293 [inline]
 qrtr_endpoint_post+0x4f1/0x1070 net/qrtr/qrtr.c:499
 qrtr_tun_write_iter+0xd0/0x140 net/qrtr/tun.c:108
 call_write_iter include/linux/fs.h:1977 [inline]
 new_sync_write+0x35d/0x5f0 fs/read_write.c:518
 vfs_write+0x5da/0x890 fs/read_write.c:605
 ksys_write+0xf4/0x1d0 fs/read_write.c:658
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x465769
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f21899d3188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000055bf00 RCX: 0000000000465769
RDX: 0000000000000020 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00000000004af65e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bf00
R13: 00007ffc7c01d90f R14: 00007f21899d3300 R15: 0000000000022000

Allocated by task 7534:
 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:427 [inline]
 ____kasan_kmalloc mm/kasan/common.c:506 [inline]
 __kasan_kmalloc+0x78/0x90 mm/kasan/common.c:515
 kasan_kmalloc include/linux/kasan.h:233 [inline]
 __do_kmalloc mm/slab.c:3695 [inline]
 __kmalloc+0x1ae/0x390 mm/slab.c:3704
 kmalloc include/linux/slab.h:559 [inline]
 kzalloc include/linux/slab.h:684 [inline]
 qrtr_tun_write_iter+0x9b/0x140 net/qrtr/tun.c:99
 call_write_iter include/linux/fs.h:1977 [inline]
 new_sync_write+0x35d/0x5f0 fs/read_write.c:518
 vfs_write+0x5da/0x890 fs/read_write.c:605
 ksys_write+0xf4/0x1d0 fs/read_write.c:658
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff888102133d40
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes to the right of
 32-byte region [ffff888102133d40, ffff888102133d60)
The buggy address belongs to the page:
page:00000000f12de73f refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888102133fc1 pfn:0x102133
flags: 0x17ffe0000000200(slab)
raw: 017ffe0000000200 ffffea00040e8bc8 ffffea0004297188 ffff888100040100
raw: ffff888102133fc1 ffff888102133000 0000000100000035 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888102133c00: fb fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
 ffff888102133c80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>ffff888102133d00: fb fb fb fb fc fc fc fc 00 00 00 00 fc fc fc fc
                                                       ^
 ffff888102133d80: fb fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
 ffff888102133e00: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
==================================================================