syzbot


WARNING: suspicious RCU usage in shmem_alloc_page

Status: fixed on 2021/11/10 00:50
Reported-by: syzbot+@syzkaller.appspotmail.com
Fix commit: 3066820034b5 rcu: Reject RCU_LOCKDEP_WARN() false positives
First crash: 515d, last: 515d

Sample crash report:
=============================
WARNING: suspicious RCU usage
5.12.0-syzkaller #0 Not tainted
-----------------------------
kernel/sched/core.c:8304 Illegal context switch in RCU-bh read-side critical section!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
1 lock held by syz-executor.5/10338:
 #0: 
ffff88802a37ea58
 (
&mm->mmap_lock
#2
){++++}-{3:3}
, at: mmap_read_lock include/linux/mmap_lock.h:117 [inline]
, at: __mm_populate+0x264/0x3e0 mm/gup.c:1430

stack backtrace:
CPU: 0 PID: 10338 Comm: syz-executor.5 Not tainted 5.12.0-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+0x141/0x1d7 lib/dump_stack.c:120
 ___might_sleep+0x229/0x2c0 kernel/sched/core.c:8304
 prepare_alloc_pages mm/page_alloc.c:4947 [inline]
 __alloc_pages_nodemask+0x48a/0x730 mm/page_alloc.c:4991
 alloc_pages_vma+0xdd/0x770 mm/mempolicy.c:2240
 shmem_alloc_page+0x11f/0x1f0 mm/shmem.c:1563
 shmem_alloc_and_acct_page+0x161/0x8a0 mm/shmem.c:1588
 shmem_getpage_gfp+0x558/0x2480 mm/shmem.c:1895
 shmem_fault+0x1fe/0x870 mm/shmem.c:2116
 __do_fault+0x10d/0x4d0 mm/memory.c:3637
 do_read_fault mm/memory.c:3939 [inline]
 do_fault mm/memory.c:4067 [inline]
 handle_pte_fault mm/memory.c:4318 [inline]
 __handle_mm_fault+0x2c87/0x4f70 mm/memory.c:4453
 handle_mm_fault+0x1bc/0x7e0 mm/memory.c:4551
 faultin_page mm/gup.c:850 [inline]
 __get_user_pages+0x7cf/0x1490 mm/gup.c:1069
 populate_vma_page_range+0x24d/0x330 mm/gup.c:1402
 __mm_populate+0x1ea/0x3e0 mm/gup.c:1450
 mm_populate include/linux/mm.h:2592 [inline]
 vm_mmap_pgoff+0x20e/0x290 mm/util.c:524
 ksys_mmap_pgoff+0xe4/0x620 mm/mmap.c:1638
 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665f9
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:00007ffad1997188 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665f9
RDX: b635773f06ebbeee RSI: 0000000000b36000 RDI: 0000000020000000
RBP: 00000000004bfce1 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000008031 R11: 0000000000000246 R12: 000000000056bf60
R13: 0000000000a9fb1f R14: 00007ffad1997300 R15: 0000000000022000

Crashes (1):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci-upstream-kasan-gce 2021/04/30 07:53 upstream d2b6f8a17919 77e2b668 .config log report info WARNING: suspicious RCU usage in shmem_alloc_page
* Struck through repros no longer work on HEAD.