The function extract_crng invokes the ChaCha20 block operation directly
on the user-provided buffer. The block operation operates on u32 words.
Thus the extract_crng function expects the buffer to be aligned to u32
as it is visible with the parameter type of extract_crng. However,
get_random_bytes uses a void pointer which may or may not be aligned.
Thus, an alignment check is necessary and the temporary buffer must be
used if the alignment to u32 is not ensured.
Cc: <stable@xxxxxxxxxxxxxxx> # v4.16+
Cc: Ted Tso <tytso@xxxxxxx>
Signed-off-by: Stephan Mueller <smueller@xxxxxxxxxx>
---
drivers/char/random.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index bd449ad52442..23f336872426 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1617,8 +1617,14 @@ static void _get_random_bytes(void *buf, int nbytes)
trace_get_random_bytes(nbytes, _RET_IP_);
while (nbytes >= CHACHA20_BLOCK_SIZE) {
- extract_crng(buf);
- buf += CHACHA20_BLOCK_SIZE;
+ if (likely((unsigned long)buf & (sizeof(tmp[0]) - 1))) {
+ extract_crng(buf);
+ buf += CHACHA20_BLOCK_SIZE;
+ } else {
+ extract_crng(tmp);
+ memcpy(buf, tmp, CHACHA20_BLOCK_SIZE);
+ }
+
nbytes -= CHACHA20_BLOCK_SIZE;
}
--
2.17.1
