From: "Jason A. Donenfeld" Jason@zx2c4.com
commit a49c010e61e1938be851f5e49ac219d49b704103 upstream.
This is called from various hwgenerator drivers, so rather than having one "safe" version for userspace and one "unsafe" version for the kernel, just make everything safe; the checks are cheap and sensible to have anyway.
Reported-by: Sultan Alsawaf sultan@kerneltoast.com Reviewed-by: Eric Biggers ebiggers@google.com Reviewed-by: Dominik Brodowski linux@dominikbrodowski.net Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/random.c | 29 +++++++++-------------------- 1 file changed, 9 insertions(+), 20 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -448,18 +448,15 @@ static void process_random_ready_list(vo spin_unlock_irqrestore(&random_ready_list_lock, flags); }
-/* - * Credit (or debit) the entropy store with n bits of entropy. - * Use credit_entropy_bits_safe() if the value comes from userspace - * or otherwise should be checked for extreme values. - */ static void credit_entropy_bits(int nbits) { int entropy_count, orig;
- if (!nbits) + if (nbits <= 0) return;
+ nbits = min(nbits, POOL_BITS); + do { orig = READ_ONCE(input_pool.entropy_count); entropy_count = min(POOL_BITS, orig + nbits); @@ -471,18 +468,6 @@ static void credit_entropy_bits(int nbit crng_reseed(&primary_crng, true); }
-static int credit_entropy_bits_safe(int nbits) -{ - if (nbits < 0) - return -EINVAL; - - /* Cap the value to avoid overflows */ - nbits = min(nbits, POOL_BITS); - - credit_entropy_bits(nbits); - return 0; -} - /********************************************************************* * * CRNG using CHACHA20 @@ -1577,7 +1562,10 @@ static long random_ioctl(struct file *f, return -EPERM; if (get_user(ent_count, p)) return -EFAULT; - return credit_entropy_bits_safe(ent_count); + if (ent_count < 0) + return -EINVAL; + credit_entropy_bits(ent_count); + return 0; case RNDADDENTROPY: if (!capable(CAP_SYS_ADMIN)) return -EPERM; @@ -1590,7 +1578,8 @@ static long random_ioctl(struct file *f, retval = write_pool((const char __user *)p, size); if (retval < 0) return retval; - return credit_entropy_bits_safe(ent_count); + credit_entropy_bits(ent_count); + return 0; case RNDZAPENTCNT: case RNDCLEARPOOL: /*