From bdfa5997e9fec2716729ce9438bdf60b1f52607f Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Mon, 28 Feb 2022 14:00:52 +0100 Subject: [PATCH] random: don't let 644 read-only sysctls be written to commit 77553cf8f44863b31da242cf24671d76ddb61597 upstream. We leave around these old sysctls for compatibility, and we keep them "writable" for compatibility, but even after writing, we should keep reporting the same value. This is consistent with how userspaces tend to use sysctl_random_write_wakeup_bits, writing to it, and then later reading from it and using the value. Cc: Theodore Ts'o Reviewed-by: Dominik Brodowski Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 116ebf50d791..884ec647f8fe 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1669,6 +1669,13 @@ static int proc_do_uuid(struct ctl_table *table, int write, void *buffer, return proc_dostring(&fake_table, 0, buffer, lenp, ppos); } +/* The same as proc_dointvec, but writes don't change anything. */ +static int proc_do_rointvec(struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos) +{ + return write ? 0 : proc_dointvec(table, 0, buffer, lenp, ppos); +} + static struct ctl_table random_table[] = { { .procname = "poolsize", @@ -1689,14 +1696,14 @@ static struct ctl_table random_table[] = { .data = &sysctl_random_write_wakeup_bits, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec, + .proc_handler = proc_do_rointvec, }, { .procname = "urandom_min_reseed_secs", .data = &sysctl_random_min_urandom_seed, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec, + .proc_handler = proc_do_rointvec, }, { .procname = "boot_id",