diff options
author | Herbert Xu <herbert@gondor.apana.org.au> | 2023-12-02 04:01:54 +0300 |
---|---|---|
committer | Herbert Xu <herbert@gondor.apana.org.au> | 2023-12-08 06:59:45 +0300 |
commit | 78aafb3884f6bc6636efcc1760c891c8500b9922 (patch) | |
tree | 89919fa3bb6a915e2c1b3eb2031581adb02fd6a5 /drivers/char/hw_random | |
parent | 01d70a4bbff20ea05cadb4c208841985a7cc6596 (diff) | |
download | linux-78aafb3884f6bc6636efcc1760c891c8500b9922.tar.xz |
hwrng: core - Fix page fault dead lock on mmap-ed hwrng
There is a dead-lock in the hwrng device read path. This triggers
when the user reads from /dev/hwrng into memory also mmap-ed from
/dev/hwrng. The resulting page fault triggers a recursive read
which then dead-locks.
Fix this by using a stack buffer when calling copy_to_user.
Reported-by: Edward Adam Davis <eadavis@qq.com>
Reported-by: syzbot+c52ab18308964d248092@syzkaller.appspotmail.com
Fixes: 9996508b3353 ("hwrng: core - Replace u32 in driver API with byte array")
Cc: <stable@vger.kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'drivers/char/hw_random')
-rw-r--r-- | drivers/char/hw_random/core.c | 34 |
1 files changed, 21 insertions, 13 deletions
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 420f155d251f..a3bbdd6e60fc 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -23,10 +23,13 @@ #include <linux/sched.h> #include <linux/sched/signal.h> #include <linux/slab.h> +#include <linux/string.h> #include <linux/uaccess.h> #define RNG_MODULE_NAME "hw_random" +#define RNG_BUFFER_SIZE (SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES) + static struct hwrng *current_rng; /* the current rng has been explicitly chosen by user via sysfs */ static int cur_rng_set_by_user; @@ -58,7 +61,7 @@ static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size, static size_t rng_buffer_size(void) { - return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES; + return RNG_BUFFER_SIZE; } static void add_early_randomness(struct hwrng *rng) @@ -209,6 +212,7 @@ static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size, static ssize_t rng_dev_read(struct file *filp, char __user *buf, size_t size, loff_t *offp) { + u8 buffer[RNG_BUFFER_SIZE]; ssize_t ret = 0; int err = 0; int bytes_read, len; @@ -236,34 +240,37 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, if (bytes_read < 0) { err = bytes_read; goto out_unlock_reading; + } else if (bytes_read == 0 && + (filp->f_flags & O_NONBLOCK)) { + err = -EAGAIN; + goto out_unlock_reading; } + data_avail = bytes_read; } - if (!data_avail) { - if (filp->f_flags & O_NONBLOCK) { - err = -EAGAIN; - goto out_unlock_reading; - } - } else { - len = data_avail; + len = data_avail; + if (len) { if (len > size) len = size; data_avail -= len; - if (copy_to_user(buf + ret, rng_buffer + data_avail, - len)) { + memcpy(buffer, rng_buffer + data_avail, len); + } + mutex_unlock(&reading_mutex); + put_rng(rng); + + if (len) { + if (copy_to_user(buf + ret, buffer, len)) { err = -EFAULT; - goto out_unlock_reading; + goto out; } size -= len; ret += len; } - mutex_unlock(&reading_mutex); - put_rng(rng); if (need_resched()) schedule_timeout_interruptible(1); @@ -274,6 +281,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, } } out: + memzero_explicit(buffer, sizeof(buffer)); return ret ? : err; out_unlock_reading: |