Hello,
syzkaller hit the following crash on a638349bf6c29433b938141f99225b160551ff48
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers
=====================================
WARNING: bad unlock balance detected!
4.15.0-rc3+ #128 Not tainted
-------------------------------------
syzkaller971460/3195 is trying to release lock (mrt_lock) at:
[<000000006898068d>] ipmr_mfc_seq_stop+0xe1/0x130 net/ipv6/ip6mr.c:553
but there are no more locks to release!
other info that might help us debug this:
1 lock held by syzkaller971460/3195:
#0: (&p->lock){+.+.}, at: [<00000000744a6565>] seq_read+0xd5/0x13d0 fs/seq_file.c:165
stack backtrace:
CPU: 1 PID: 3195 Comm: syzkaller971460 Not tainted 4.15.0-rc3+ #128
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
print_unlock_imbalance_bug+0x12f/0x140 kernel/locking/lockdep.c:3561
__lock_release kernel/locking/lockdep.c:3775 [inline]
lock_release+0x5f9/0xda0 kernel/locking/lockdep.c:4023
__raw_read_unlock include/linux/rwlock_api_smp.h:225 [inline]
_raw_read_unlock+0x1a/0x30 kernel/locking/spinlock.c:255
ipmr_mfc_seq_stop+0xe1/0x130 net/ipv6/ip6mr.c:553
traverse+0x3bc/0xa00 fs/seq_file.c:135
seq_read+0x96a/0x13d0 fs/seq_file.c:189
proc_reg_read+0xef/0x170 fs/proc/inode.c:217
do_loop_readv_writev fs/read_write.c:673 [inline]
do_iter_read+0x3db/0x5b0 fs/read_write.c:897
compat_readv+0x1bf/0x270 fs/read_write.c:1140
do_compat_preadv64+0xdc/0x100 fs/read_write.c:1189
C_SYSC_preadv fs/read_write.c:1209 [inline]
compat_SyS_preadv+0x3b/0x50 fs/read_write.c:1203
do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125
RIP: 0023:0xf7f73c79
RSP: 002b:00000000e574a15c EFLAGS: 00000292 ORIG_RAX: 000000000000014d
RAX: ffffffffffffffda RBX: 000000000000000f RCX: 0000000020a3afb0
RDX: 0000000000000001 RSI: 0000000000000067 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
BUG: sleeping function called from invalid context at lib/usercopy.c:25
in_atomic(): 1, irqs_disabled(): 0, pid: 3195, name: syzkaller971460
INFO: lockdep is turned off.
CPU: 1 PID: 3195 Comm: syzkaller971460 Not tainted 4.15.0-rc3+ #128
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
___might_sleep+0x2b2/0x470 kernel/sched/core.c:6060
__might_sleep+0x95/0x190 kernel/sched/core.c:6013
__might_fault+0xab/0x1d0 mm/memory.c:4525
_copy_to_user+0x2c/0xc0 lib/usercopy.c:25
copy_to_user include/linux/uaccess.h:155 [inline]
seq_read+0xcb4/0x13d0 fs/seq_file.c:279
proc_reg_read+0xef/0x170 fs/proc/inode.c:217
do_loop_readv_writev fs/read_write.c:673 [inline]
do_iter_read+0x3db/0x5b0 fs/read_write.c:897
compat_readv+0x1bf/0x270 fs/read_write.c:1140
do_compat_preadv64+0xdc/0x100 fs/read_write.c:1189
C_SYSC_preadv fs/read_write.c:1209 [inline]
compat_SyS_preadv+0x3b/0x50 fs/read_write.c:1203
do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125
RIP: 0023:0xf7f73c79
RSP: 002b:00000000e574a15c EFLAGS: 00000292 ORIG_RAX: 000000000000014d
RAX: ffffffffffffffda RBX: 000000000000000f RCX: 0000000020a3afb0
RDX: 0000000000000001 RSI: 0000000000000067 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
WARNING: CPU: 1 PID: 3195 at lib/usercopy.c:26 _copy_to_user+0xb5/0xc0 lib/usercopy.c:26
---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@googlegroups.com.
Please credit me with: Reported-by: syzbot [off-list ref]
syzbot will keep track of this bug report.
Once a fix for this bug is merged into any tree, reply to this email with:
#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug report.
Note: all commands must start from beginning of the line in the email body.
From: Eric Biggers <hidden> Date: 2018-01-31 00:30:28
On Fri, Dec 15, 2017 at 11:52:01PM -0800, syzbot wrote:
Hello,
syzkaller hit the following crash on
a638349bf6c29433b938141f99225b160551ff48
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers
=====================================
WARNING: bad unlock balance detected!
4.15.0-rc3+ #128 Not tainted
-------------------------------------
syzkaller971460/3195 is trying to release lock (mrt_lock) at:
[<000000006898068d>] ipmr_mfc_seq_stop+0xe1/0x130 net/ipv6/ip6mr.c:553
but there are no more locks to release!
other info that might help us debug this:
1 lock held by syzkaller971460/3195:
#0: (&p->lock){+.+.}, at: [<00000000744a6565>] seq_read+0xd5/0x13d0
fs/seq_file.c:165
stack backtrace:
CPU: 1 PID: 3195 Comm: syzkaller971460 Not tainted 4.15.0-rc3+ #128
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
print_unlock_imbalance_bug+0x12f/0x140 kernel/locking/lockdep.c:3561
__lock_release kernel/locking/lockdep.c:3775 [inline]
lock_release+0x5f9/0xda0 kernel/locking/lockdep.c:4023
__raw_read_unlock include/linux/rwlock_api_smp.h:225 [inline]
_raw_read_unlock+0x1a/0x30 kernel/locking/spinlock.c:255
ipmr_mfc_seq_stop+0xe1/0x130 net/ipv6/ip6mr.c:553
traverse+0x3bc/0xa00 fs/seq_file.c:135
seq_read+0x96a/0x13d0 fs/seq_file.c:189
proc_reg_read+0xef/0x170 fs/proc/inode.c:217
do_loop_readv_writev fs/read_write.c:673 [inline]
do_iter_read+0x3db/0x5b0 fs/read_write.c:897
compat_readv+0x1bf/0x270 fs/read_write.c:1140
do_compat_preadv64+0xdc/0x100 fs/read_write.c:1189
C_SYSC_preadv fs/read_write.c:1209 [inline]
compat_SyS_preadv+0x3b/0x50 fs/read_write.c:1203
do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125
RIP: 0023:0xf7f73c79
RSP: 002b:00000000e574a15c EFLAGS: 00000292 ORIG_RAX: 000000000000014d
RAX: ffffffffffffffda RBX: 000000000000000f RCX: 0000000020a3afb0
RDX: 0000000000000001 RSI: 0000000000000067 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
BUG: sleeping function called from invalid context at lib/usercopy.c:25
in_atomic(): 1, irqs_disabled(): 0, pid: 3195, name: syzkaller971460
INFO: lockdep is turned off.
CPU: 1 PID: 3195 Comm: syzkaller971460 Not tainted 4.15.0-rc3+ #128
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
___might_sleep+0x2b2/0x470 kernel/sched/core.c:6060
__might_sleep+0x95/0x190 kernel/sched/core.c:6013
__might_fault+0xab/0x1d0 mm/memory.c:4525
_copy_to_user+0x2c/0xc0 lib/usercopy.c:25
copy_to_user include/linux/uaccess.h:155 [inline]
seq_read+0xcb4/0x13d0 fs/seq_file.c:279
proc_reg_read+0xef/0x170 fs/proc/inode.c:217
do_loop_readv_writev fs/read_write.c:673 [inline]
do_iter_read+0x3db/0x5b0 fs/read_write.c:897
compat_readv+0x1bf/0x270 fs/read_write.c:1140
do_compat_preadv64+0xdc/0x100 fs/read_write.c:1189
C_SYSC_preadv fs/read_write.c:1209 [inline]
compat_SyS_preadv+0x3b/0x50 fs/read_write.c:1203
do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125
RIP: 0023:0xf7f73c79
RSP: 002b:00000000e574a15c EFLAGS: 00000292 ORIG_RAX: 000000000000014d
RAX: ffffffffffffffda RBX: 000000000000000f RCX: 0000000020a3afb0
RDX: 0000000000000001 RSI: 0000000000000067 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
WARNING: CPU: 1 PID: 3195 at lib/usercopy.c:26 _copy_to_user+0xb5/0xc0
lib/usercopy.c:26
---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@googlegroups.com.
Please credit me with: Reported-by: syzbot [off-list ref]
syzbot will keep track of this bug report.
Once a fix for this bug is merged into any tree, reply to this email with:
#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug
report.
Note: all commands must start from beginning of the line in the email body.
This is still happening. Here's a simplified reproducer, assuming that
CONFIG_IPV6_MROUTE and CONFIG_PROVE_LOCKING are enabled:
#include <fcntl.h>
#include <linux/mroute6.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <unistd.h>
int main()
{
struct mf6cctl ctl = { };
int cachefd = open("/proc/self/net/ip6_mr_cache", O_RDONLY);
int sockfd = socket(AF_INET6, SOCK_RAW, 0x3aul);
char buf[2];
if (fork() == 0) {
for (;;)
pread(cachefd, buf, 2, 103);
} else {
for (;;) {
setsockopt(sockfd, SOL_IPV6, MRT6_ADD_MFC,
&ctl, sizeof(ctl));
}
}
}
On Wed, Jan 31, 2018 at 3:29 PM, Nikolay Aleksandrov
[off-list ref] wrote:
When we dump the ip6mr mfc entries via proc, we initialize an iterator
with the table to dump but we don't clear the cache pointer which might
be initialized from a prior read on the same descriptor that ended. This
can result in lock imbalance (an unnecessary unlock) leading to other
crashes and hangs. Clear the cache pointer like ipmr does to fix the issue.
Thanks for the reliable reproducer.
Here's syzbot's trace:
WARNING: bad unlock balance detected!
4.15.0-rc3+ #128 Not tainted
syzkaller971460/3195 is trying to release lock (mrt_lock) at:
[<000000006898068d>] ipmr_mfc_seq_stop+0xe1/0x130 net/ipv6/ip6mr.c:553
but there are no more locks to release!
other info that might help us debug this:
1 lock held by syzkaller971460/3195:
#0: (&p->lock){+.+.}, at: [<00000000744a6565>] seq_read+0xd5/0x13d0
fs/seq_file.c:165
stack backtrace:
CPU: 1 PID: 3195 Comm: syzkaller971460 Not tainted 4.15.0-rc3+ #128
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
print_unlock_imbalance_bug+0x12f/0x140 kernel/locking/lockdep.c:3561
__lock_release kernel/locking/lockdep.c:3775 [inline]
lock_release+0x5f9/0xda0 kernel/locking/lockdep.c:4023
__raw_read_unlock include/linux/rwlock_api_smp.h:225 [inline]
_raw_read_unlock+0x1a/0x30 kernel/locking/spinlock.c:255
ipmr_mfc_seq_stop+0xe1/0x130 net/ipv6/ip6mr.c:553
traverse+0x3bc/0xa00 fs/seq_file.c:135
seq_read+0x96a/0x13d0 fs/seq_file.c:189
proc_reg_read+0xef/0x170 fs/proc/inode.c:217
do_loop_readv_writev fs/read_write.c:673 [inline]
do_iter_read+0x3db/0x5b0 fs/read_write.c:897
compat_readv+0x1bf/0x270 fs/read_write.c:1140
do_compat_preadv64+0xdc/0x100 fs/read_write.c:1189
C_SYSC_preadv fs/read_write.c:1209 [inline]
compat_SyS_preadv+0x3b/0x50 fs/read_write.c:1203
do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125
RIP: 0023:0xf7f73c79
RSP: 002b:00000000e574a15c EFLAGS: 00000292 ORIG_RAX: 000000000000014d
RAX: ffffffffffffffda RBX: 000000000000000f RCX: 0000000020a3afb0
RDX: 0000000000000001 RSI: 0000000000000067 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
BUG: sleeping function called from invalid context at lib/usercopy.c:25
in_atomic(): 1, irqs_disabled(): 0, pid: 3195, name: syzkaller971460
INFO: lockdep is turned off.
CPU: 1 PID: 3195 Comm: syzkaller971460 Not tainted 4.15.0-rc3+ #128
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
___might_sleep+0x2b2/0x470 kernel/sched/core.c:6060
__might_sleep+0x95/0x190 kernel/sched/core.c:6013
__might_fault+0xab/0x1d0 mm/memory.c:4525
_copy_to_user+0x2c/0xc0 lib/usercopy.c:25
copy_to_user include/linux/uaccess.h:155 [inline]
seq_read+0xcb4/0x13d0 fs/seq_file.c:279
proc_reg_read+0xef/0x170 fs/proc/inode.c:217
do_loop_readv_writev fs/read_write.c:673 [inline]
do_iter_read+0x3db/0x5b0 fs/read_write.c:897
compat_readv+0x1bf/0x270 fs/read_write.c:1140
do_compat_preadv64+0xdc/0x100 fs/read_write.c:1189
C_SYSC_preadv fs/read_write.c:1209 [inline]
compat_SyS_preadv+0x3b/0x50 fs/read_write.c:1203
do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125
RIP: 0023:0xf7f73c79
RSP: 002b:00000000e574a15c EFLAGS: 00000292 ORIG_RAX: 000000000000014d
RAX: ffffffffffffffda RBX: 000000000000000f RCX: 0000000020a3afb0
RDX: 0000000000000001 RSI: 0000000000000067 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
WARNING: CPU: 1 PID: 3195 at lib/usercopy.c:26 _copy_to_user+0xb5/0xc0
lib/usercopy.c:26
Reported-by: syzbot <redacted>
Signed-off-by: Nikolay Aleksandrov <redacted>
---
v2: make sure the trace doesn't ruin the patch
No fixes tag because it seems this has been there forever.
Don't we need to Cc stable 2.6 in this case or something like this. We
want it to be backported.
From: Nikolay Aleksandrov <hidden> Date: 2018-01-31 14:52:48
On 31/01/18 16:49, Dmitry Vyukov wrote:
On Wed, Jan 31, 2018 at 3:29 PM, Nikolay Aleksandrov
[off-list ref] wrote:
quoted
When we dump the ip6mr mfc entries via proc, we initialize an iterator
with the table to dump but we don't clear the cache pointer which might
be initialized from a prior read on the same descriptor that ended. This
can result in lock imbalance (an unnecessary unlock) leading to other
crashes and hangs. Clear the cache pointer like ipmr does to fix the issue.
Thanks for the reliable reproducer.
[snip]
quoted
Reported-by: syzbot <redacted>
Signed-off-by: Nikolay Aleksandrov <redacted>
---
v2: make sure the trace doesn't ruin the patch
No fixes tag because it seems this has been there forever.
Don't we need to Cc stable 2.6 in this case or something like this. We
want it to be backported.
AFAIK Dave takes care of queueing the patches for stable backports and
maintainers get them from his stable queue.
On Wed, Jan 31, 2018 at 3:52 PM, Nikolay Aleksandrov
[off-list ref] wrote:
On 31/01/18 16:49, Dmitry Vyukov wrote:
quoted
On Wed, Jan 31, 2018 at 3:29 PM, Nikolay Aleksandrov
[off-list ref] wrote:
quoted
When we dump the ip6mr mfc entries via proc, we initialize an iterator
with the table to dump but we don't clear the cache pointer which might
be initialized from a prior read on the same descriptor that ended. This
can result in lock imbalance (an unnecessary unlock) leading to other
crashes and hangs. Clear the cache pointer like ipmr does to fix the issue.
Thanks for the reliable reproducer.
[snip]
quoted
quoted
Reported-by: syzbot <redacted>
Signed-off-by: Nikolay Aleksandrov <redacted>
---
v2: make sure the trace doesn't ruin the patch
No fixes tag because it seems this has been there forever.
Don't we need to Cc stable 2.6 in this case or something like this. We
want it to be backported.
AFAIK Dave takes care of queueing the patches for stable backports and
maintainers get them from his stable queue.
From: David Miller <davem@davemloft.net> Date: 2018-01-31 15:34:02
From: Nikolay Aleksandrov <redacted>
Date: Wed, 31 Jan 2018 16:29:30 +0200
When we dump the ip6mr mfc entries via proc, we initialize an iterator
with the table to dump but we don't clear the cache pointer which might
be initialized from a prior read on the same descriptor that ended. This
can result in lock imbalance (an unnecessary unlock) leading to other
crashes and hangs. Clear the cache pointer like ipmr does to fix the issue.
Thanks for the reliable reproducer.
Here's syzbot's trace:
...
Reported-by: syzbot <redacted>
Signed-off-by: Nikolay Aleksandrov <redacted>
---
v2: make sure the trace doesn't ruin the patch
No fixes tag because it seems this has been there forever.