From a98406e22c12e514bac28fec0a49dc793edaf3a8 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Sat, 23 Aug 2014 17:03:28 +0200 Subject: random32: improvements to prandom_bytes MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This patch addresses a couple of minor items, mostly addesssing prandom_bytes(): 1) prandom_bytes{,_state}() should use size_t for length arguments, 2) We can use put_unaligned() when filling the array instead of open coding it [ perhaps some archs will further benefit from their own arch specific implementation when GCC cannot make up for it ], 3) Fix a typo, 4) Better use unsigned int as type for getting the arch seed, 5) Make use of prandom_u32_max() for timer slack. Regarding the change to put_unaligned(), callers of prandom_bytes() which internally invoke prandom_bytes_state(), don't bother as they expect the array to be filled randomly and don't have any control of the internal state what-so-ever (that's also why we have periodic reseeding there, etc), so they really don't care. Now for the direct callers of prandom_bytes_state(), which are solely located in test cases for MTD devices, that is, drivers/mtd/tests/{oobtest.c,pagetest.c,subpagetest.c}: These tests basically fill a test write-vector through prandom_bytes_state() with an a-priori defined seed each time and write that to a MTD device. Later on, they set up a read-vector and read back that blocks from the device. So in the verification phase, the write-vector is being re-setup [ so same seed and prandom_bytes_state() called ], and then memcmp()'ed against the read-vector to check if the data is the same. Akinobu, Lothar and I also tested this patch and it runs through the 3 relevant MTD test cases w/o any errors on the nandsim device (simulator for MTD devs) for x86_64, ppc64, ARM (i.MX28, i.MX53 and i.MX6): # modprobe nandsim first_id_byte=0x20 second_id_byte=0xac \ third_id_byte=0x00 fourth_id_byte=0x15 # modprobe mtd_oobtest dev=0 # modprobe mtd_pagetest dev=0 # modprobe mtd_subpagetest dev=0 We also don't have any users depending directly on a particular result of the PRNG (except the PRNG self-test itself), and that's just fine as it e.g. allowed us easily to do things like upgrading from taus88 to taus113. Signed-off-by: Daniel Borkmann Tested-by: Akinobu Mita Tested-by: Lothar Waßmann Cc: Hannes Frederic Sowa Signed-off-by: David S. Miller --- include/linux/random.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/random.h b/include/linux/random.h index 57fbbffd77a0..b05856e16b75 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -26,7 +26,7 @@ unsigned int get_random_int(void); unsigned long randomize_range(unsigned long start, unsigned long end, unsigned long len); u32 prandom_u32(void); -void prandom_bytes(void *buf, int nbytes); +void prandom_bytes(void *buf, size_t nbytes); void prandom_seed(u32 seed); void prandom_reseed_late(void); @@ -35,7 +35,7 @@ struct rnd_state { }; u32 prandom_u32_state(struct rnd_state *state); -void prandom_bytes_state(struct rnd_state *state, void *buf, int nbytes); +void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes); /** * prandom_u32_max - returns a pseudo-random number in interval [0, ep_ro) -- cgit v1.2.3