This is a note to let you know that I've just added the patch titled
random: remove preempt disabled region
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
random-remove-preempt-disabled-region.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Jun 16 07:08:33 PM CEST 2022
From: Ingo Molnar <mingo@xxxxxxx>
Date: Sun, 22 Jul 2018 10:51:50 -0400
Subject: random: remove preempt disabled region
From: Ingo Molnar <mingo@xxxxxxx>
commit b34fbaa9289328c7aec67d2b8b8b7d02bc61c67d upstream.
No need to keep preemption disabled across the whole function.
mix_pool_bytes() uses a spin_lock() to protect the pool and there are
other places like write_pool() whhich invoke mix_pool_bytes() without
disabling preemption.
credit_entropy_bits() is invoked from other places like
add_hwgenerator_randomness() without disabling preemption.
Before commit 95b709b6be49 ("random: drop trickle mode") the function
used __this_cpu_inc_return() which would require disabled preemption.
The preempt_disable() section was added in commit 43d5d3018c37 ("[PATCH]
random driver preempt robustness", history tree). It was claimed that
the code relied on "vt_ioctl() being called under BKL".
Cc: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
[bigeasy: enhance the commit message]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/char/random.c | 4 ----
1 file changed, 4 deletions(-)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1136,8 +1136,6 @@ static void add_timer_randomness(struct
} sample;
long delta, delta2, delta3;
- preempt_disable();
-
sample.jiffies = jiffies;
sample.cycles = random_get_entropy();
sample.num = num;
@@ -1175,8 +1173,6 @@ static void add_timer_randomness(struct
* and limit entropy entimate to 12 bits.
*/
credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
-
- preempt_enable();
}
void add_input_randomness(unsigned int type, unsigned int code,
Patches currently in stable-queue which might be from mingo@xxxxxxx are
queue-4.14/random-remove-preempt-disabled-region.patch
