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| author | Jason A. Donenfeld <Jason@zx2c4.com> | 2022-09-08 17:14:00 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-10-26 14:19:19 +0300 |
| commit | 34e9ae783d63d758a1e8cd365cd3a04ec188d96a (patch) | |
| tree | 5374d4f0ee732850ce2439085328b4ca9bbbbd52 | |
| parent | d7950203eb68b8d440e213487479042e3da21a1c (diff) | |
| download | linux-34e9ae783d63d758a1e8cd365cd3a04ec188d96a.tar.xz | |
random: restore O_NONBLOCK support
commit cd4f24ae9404fd31fc461066e57889be3b68641b upstream.
Prior to 5.6, when /dev/random was opened with O_NONBLOCK, it would
return -EAGAIN if there was no entropy. When the pools were unified in
5.6, this was lost. The post 5.6 behavior of blocking until the pool is
initialized, and ignoring O_NONBLOCK in the process, went unnoticed,
with no reports about the regression received for two and a half years.
However, eventually this indeed did break somebody's userspace.
So we restore the old behavior, by returning -EAGAIN if the pool is not
initialized. Unlike the old /dev/random, this can only occur during
early boot, after which it never blocks again.
In order to make this O_NONBLOCK behavior consistent with other
expectations, also respect users reading with preadv2(RWF_NOWAIT) and
similar.
Fixes: 30c08efec888 ("random: make /dev/random be almost like /dev/urandom")
Reported-by: Guozihua <guozihua@huawei.com>
Reported-by: Zhongguohua <zhongguohua1@huawei.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andrew Lutomirski <luto@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/char/mem.c | 4 | ||||
| -rw-r--r-- | drivers/char/random.c | 5 |
2 files changed, 7 insertions, 2 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 54b86490d9ca..9f1caa7eb8d1 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -893,8 +893,8 @@ static const struct memdev { #endif [5] = { "zero", 0666, &zero_fops, 0 }, [7] = { "full", 0666, &full_fops, 0 }, - [8] = { "random", 0666, &random_fops, 0 }, - [9] = { "urandom", 0666, &urandom_fops, 0 }, + [8] = { "random", 0666, &random_fops, FMODE_NOWAIT }, + [9] = { "urandom", 0666, &urandom_fops, FMODE_NOWAIT }, #ifdef CONFIG_PRINTK [11] = { "kmsg", 0644, &kmsg_fops, 0 }, #endif diff --git a/drivers/char/random.c b/drivers/char/random.c index 3d8259a78469..e5b331006f17 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1294,6 +1294,11 @@ static ssize_t random_read_iter(struct kiocb *kiocb, struct iov_iter *iter) { int ret; + if (!crng_ready() && + ((kiocb->ki_flags & IOCB_NOWAIT) || + (kiocb->ki_filp->f_flags & O_NONBLOCK))) + return -EAGAIN; + ret = wait_for_random_bytes(); if (ret != 0) return ret; |