[PATCH AUTOSEL 4.19 01/87] locks: Fix UBSAN undefined behaviour in flock64_to_posix_lock

[PATCH AUTOSEL 4.19 01/87] locks: Fix UBSAN undefined behaviour in flock64_to_posix_lock

[Sasha Levin]

From: Luo Meng <luomeng12@huawei.com>

[ Upstream commit 16238415eb9886328a89fe7a3cb0b88c7335fe16 ]

When the sum of fl->fl_start and l->l_len overflows,
UBSAN shows the following warning:

UBSAN: Undefined behaviour in fs/locks.c:482:29
signed integer overflow: 2 + 9223372036854775806
cannot be represented in type 'long long int'
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xe4/0x14e lib/dump_stack.c:118
 ubsan_epilogue+0xe/0x81 lib/ubsan.c:161
 handle_overflow+0x193/0x1e2 lib/ubsan.c:192
 flock64_to_posix_lock fs/locks.c:482 [inline]
 flock_to_posix_lock+0x595/0x690 fs/locks.c:515
 fcntl_setlk+0xf3/0xa90 fs/locks.c:2262
 do_fcntl+0x456/0xf60 fs/fcntl.c:387
 __do_sys_fcntl fs/fcntl.c:483 [inline]
 __se_sys_fcntl fs/fcntl.c:468 [inline]
 __x64_sys_fcntl+0x12d/0x180 fs/fcntl.c:468
 do_syscall_64+0xc8/0x5a0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Fix it by parenthesizing 'l->l_len - 1'.

Signed-off-by: Luo Meng <luomeng12@huawei.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/locks.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/locks.c b/fs/locks.c
index 28270e74be342..465917362eca3 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -479,7 +479,7 @@ static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
 	if (l->l_len > 0) {
 		if (l->l_len - 1 > OFFSET_MAX - fl->fl_start)
 			return -EOVERFLOW;
-		fl->fl_end = fl->fl_start + l->l_len - 1;
+		fl->fl_end = fl->fl_start + (l->l_len - 1);
 
 	} else if (l->l_len < 0) {
 		if (fl->fl_start + l->l_len < 0)
-- 
2.27.0

[PATCH AUTOSEL 4.19 07/87] fcntl: Fix potential deadlock in send_sig{io, urg}()

[Sasha Levin]

From: Boqun Feng <boqun.feng@gmail.com>

[ Upstream commit 8d1ddb5e79374fb277985a6b3faa2ed8631c5b4c ]

Syzbot reports a potential deadlock found by the newly added recursive
read deadlock detection in lockdep:

[...] ========================================================
[...] WARNING: possible irq lock inversion dependency detected
[...] 5.9.0-rc2-syzkaller #0 Not tainted
[...] --------------------------------------------------------
[...] syz-executor.1/10214 just changed the state of lock:
[...] ffff88811f506338 (&f->f_owner.lock){.+..}-{2:2}, at: send_sigurg+0x1d/0x200
[...] but this lock was taken by another, HARDIRQ-safe lock in the past:
[...]  (&dev->event_lock){-...}-{2:2}
[...]
[...]
[...] and interrupts could create inverse lock ordering between them.
[...]
[...]
[...] other info that might help us debug this:
[...] Chain exists of:
[...]   &dev->event_lock --> &new->fa_lock --> &f->f_owner.lock
[...]
[...]  Possible interrupt unsafe locking scenario:
[...]
[...]        CPU0                    CPU1
[...]        ----                    ----
[...]   lock(&f->f_owner.lock);
[...]                                local_irq_disable();
[...]                                lock(&dev->event_lock);
[...]                                lock(&new->fa_lock);
[...]   <Interrupt>
[...]     lock(&dev->event_lock);
[...]
[...]  *** DEADLOCK ***

The corresponding deadlock case is as followed:

	CPU 0		CPU 1		CPU 2
	read_lock(&fown->lock);
			spin_lock_irqsave(&dev->event_lock, ...)
					write_lock_irq(&filp->f_owner.lock); // wait for the lock
			read_lock(&fown-lock); // have to wait until the writer release
					       // due to the fairness
	<interrupted>
	spin_lock_irqsave(&dev->event_lock); // wait for the lock

The lock dependency on CPU 1 happens if there exists a call sequence:

	input_inject_event():
	  spin_lock_irqsave(&dev->event_lock,...);
	  input_handle_event():
	    input_pass_values():
	      input_to_handler():
	        handler->event(): // evdev_event()
	          evdev_pass_values():
	            spin_lock(&client->buffer_lock);
	            __pass_event():
	              kill_fasync():
	                kill_fasync_rcu():
	                  read_lock(&fa->fa_lock);
	                  send_sigio():
	                    read_lock(&fown->lock);

To fix this, make the reader in send_sigurg() and send_sigio() use
read_lock_irqsave() and read_lock_irqrestore().

Reported-by: syzbot+22e87cdf94021b984aa6@syzkaller.appspotmail.com
Reported-by: syzbot+c5e32344981ad9f33750@syzkaller.appspotmail.com
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/fcntl.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/fcntl.c b/fs/fcntl.c
index 4137d96534a6c..e039af1872ab2 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -779,9 +779,10 @@ void send_sigio(struct fown_struct *fown, int fd, int band)
 {
 	struct task_struct *p;
 	enum pid_type type;
+	unsigned long flags;
 	struct pid *pid;
 	
-	read_lock(&fown->lock);
+	read_lock_irqsave(&fown->lock, flags);
 
 	type = fown->pid_type;
 	pid = fown->pid;
@@ -802,7 +803,7 @@ void send_sigio(struct fown_struct *fown, int fd, int band)
 		read_unlock(&tasklist_lock);
 	}
  out_unlock_fown:
-	read_unlock(&fown->lock);
+	read_unlock_irqrestore(&fown->lock, flags);
 }
 
 static void send_sigurg_to_task(struct task_struct *p,
@@ -817,9 +818,10 @@ int send_sigurg(struct fown_struct *fown)
 	struct task_struct *p;
 	enum pid_type type;
 	struct pid *pid;
+	unsigned long flags;
 	int ret = 0;
 	
-	read_lock(&fown->lock);
+	read_lock_irqsave(&fown->lock, flags);
 
 	type = fown->pid_type;
 	pid = fown->pid;
@@ -842,7 +844,7 @@ int send_sigurg(struct fown_struct *fown)
 		read_unlock(&tasklist_lock);
 	}
  out_unlock_fown:
-	read_unlock(&fown->lock);
+	read_unlock_irqrestore(&fown->lock, flags);
 	return ret;
 }
 
-- 
2.27.0