diff options
| author | Akinobu Mita <akinobu.mita@gmail.com> | 2024-12-08 17:24:15 +0300 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2025-01-13 07:21:00 +0300 |
| commit | e9bc360b105c2042db30c36ed1c5ca48dcc7f84b (patch) | |
| tree | fcb289b53b70ab68c6fa7a2fdadeb30fa8186641 | |
| parent | 3735c5225b97cb57745afd151904d08847b09cc7 (diff) | |
| download | linux-e9bc360b105c2042db30c36ed1c5ca48dcc7f84b.tar.xz | |
fault-inject: use prandom where cryptographically secure randomness is not needed
Currently get_random*() is used to determine the probability of fault
injection, but cryptographically secure random numbers are not required.
There is no big problem in using prandom instead of get_random*() to
determine the probability of fault injection, and it also avoids acquiring
a spinlock, which is unsafe in some contexts.
[akpm@linux-foundation.org: tweak and reflow comment]
Link: https://lore.kernel.org/lkml/20241129120939.GG35539@noisy.programming.kicks-ass.net
Link: https://lkml.kernel.org/r/20241208142415.205960-1-akinobu.mita@gmail.com
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | lib/fault-inject.c | 28 |
1 files changed, 26 insertions, 2 deletions
diff --git a/lib/fault-inject.c b/lib/fault-inject.c index 52eb6ba29698..999053fa133e 100644 --- a/lib/fault-inject.c +++ b/lib/fault-inject.c @@ -1,7 +1,7 @@ // SPDX-License-Identifier: GPL-2.0-only #include <linux/kernel.h> #include <linux/init.h> -#include <linux/random.h> +#include <linux/prandom.h> #include <linux/debugfs.h> #include <linux/sched.h> #include <linux/stat.h> @@ -13,6 +13,24 @@ #include <linux/fault-inject.h> /* + * The should_fail() functions use prandom instead of the normal Linux RNG + * since they don't need cryptographically secure random numbers. + */ +static DEFINE_PER_CPU(struct rnd_state, fault_rnd_state); + +static u32 fault_prandom_u32_below_100(void) +{ + struct rnd_state *state; + u32 res; + + state = &get_cpu_var(fault_rnd_state); + res = prandom_u32_state(state); + put_cpu_var(fault_rnd_state); + + return res % 100; +} + +/* * setup_fault_attr() is a helper function for various __setup handlers, so it * returns 0 on error, because that is what __setup handlers do. */ @@ -31,6 +49,8 @@ int setup_fault_attr(struct fault_attr *attr, char *str) return 0; } + prandom_init_once(&fault_rnd_state); + attr->probability = probability; attr->interval = interval; atomic_set(&attr->times, times); @@ -146,7 +166,7 @@ bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags) return false; } - if (attr->probability <= get_random_u32_below(100)) + if (attr->probability <= fault_prandom_u32_below_100()) return false; fail: @@ -219,6 +239,8 @@ struct dentry *fault_create_debugfs_attr(const char *name, if (IS_ERR(dir)) return dir; + prandom_init_once(&fault_rnd_state); + debugfs_create_ul("probability", mode, dir, &attr->probability); debugfs_create_ul("interval", mode, dir, &attr->interval); debugfs_create_atomic_t("times", mode, dir, &attr->times); @@ -431,6 +453,8 @@ static const struct config_item_type fault_config_type = { void fault_config_init(struct fault_config *config, const char *name) { + prandom_init_once(&fault_rnd_state); + config_group_init_type_name(&config->group, name, &fault_config_type); } EXPORT_SYMBOL_GPL(fault_config_init); |