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random: don't let 644 read-only sysctls be written to 

commit 77553cf8f4 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 <tytso@mit.edu>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jason A. Donenfeld 2022-02-28 14:00:52 +01:00 committed by Greg Kroah-Hartman
parent eca9204717
commit bdfa5997e9
1 changed files with 9 additions and 2 deletions
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11
drivers/char/random.c
View File

@ -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",