From: "Jason A. Donenfeld" Jason@zx2c4.com
commit a254a0e4093fce8c832414a83940736067eed515 upstream.
Now that have_bytes is never modified, we can simplify this function. First, we move the check for negative entropy_count to be first. That ensures that subsequent reads of this will be non-negative. Then, have_bytes and ibytes can be folded into their one use site in the min_t() function.
Suggested-by: Dominik Brodowski linux@dominikbrodowski.net 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 | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1293,7 +1293,7 @@ EXPORT_SYMBOL_GPL(add_disk_randomness); */ static size_t account(size_t nbytes, int min) { - int entropy_count, orig, have_bytes; + int entropy_count, orig; size_t ibytes, nfrac;
BUG_ON(input_pool.entropy_count > POOL_FRACBITS); @@ -1301,20 +1301,15 @@ static size_t account(size_t nbytes, int /* Can we pull enough? */ retry: entropy_count = orig = READ_ONCE(input_pool.entropy_count); - ibytes = nbytes; - /* never pull more than available */ - have_bytes = entropy_count >> (POOL_ENTROPY_SHIFT + 3); - - if (have_bytes < 0) - have_bytes = 0; - ibytes = min_t(size_t, ibytes, have_bytes); - if (ibytes < min) - ibytes = 0; - if (WARN_ON(entropy_count < 0)) { pr_warn("negative entropy count: count %d\n", entropy_count); entropy_count = 0; } + + /* never pull more than available */ + ibytes = min_t(size_t, nbytes, entropy_count >> (POOL_ENTROPY_SHIFT + 3)); + if (ibytes < min) + ibytes = 0; nfrac = ibytes << (POOL_ENTROPY_SHIFT + 3); if ((size_t)entropy_count > nfrac) entropy_count -= nfrac;