From 1ab87298cb59b649d8d648d25dc15b36ab865f5a Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Fri, 27 Nov 2015 16:50:43 +0100 Subject: [PATCH] hwrng: core - sleep interruptible in read hwrng kthread can be waiting via hwrng_fillfn for some data from a rng like virtio-rng: hwrng D ffff880093e17798 0 382 2 0x00000000 ... Call Trace: [] wait_for_completion_killable+0x96/0x210 [] virtio_read+0x57/0xf0 [virtio_rng] [] hwrng_fillfn+0x75/0x130 [] kthread+0xf3/0x110 And when some user program tries to read the /dev node in this state, we get: rngd D ffff880093e17798 0 762 1 0x00000004 ... Call Trace: [] mutex_lock_nested+0x15c/0x3e0 [] rng_dev_read+0x6e/0x240 [] __vfs_read+0x28/0xe0 [] vfs_read+0x83/0x130 And this is indeed unkillable. So use mutex_lock_interruptible instead of mutex_lock in rng_dev_read and exit immediatelly when interrupted. And possibly return already read data, if any (as POSIX allows). v2: use ERESTARTSYS instead of EINTR Signed-off-by: Jiri Slaby Cc: Matt Mackall Cc: Herbert Xu Cc: Signed-off-by: Herbert Xu --- drivers/char/hw_random/core.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 6f497aa1b276..9203f2d130c0 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -238,7 +238,10 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, goto out; } - mutex_lock(&reading_mutex); + if (mutex_lock_interruptible(&reading_mutex)) { + err = -ERESTARTSYS; + goto out_put; + } if (!data_avail) { bytes_read = rng_get_data(rng, rng_buffer, rng_buffer_size(), @@ -288,6 +291,7 @@ out: out_unlock_reading: mutex_unlock(&reading_mutex); +out_put: put_rng(rng); goto out; } -- 2.20.1