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random: cleanup UUID handling

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Rather than hard coding various lengths, we can use the right constants.
Strings should be `char *` while buffers should be `u8 *`. Rather than
have a nonsensical and unused maxlength, just remove it. Finally, use
snprintf instead of sprintf, just out of good hygiene.

As well, remove the old comment about returning a binary UUID via the
binary sysctl syscall. That syscall was removed from the kernel in 5.5,
and actually, the "uuid_strategy" function and related infrastructure
for even serving it via the binary sysctl syscall was removed with
894d249115 ("sysctl drivers: Remove dead binary sysctl support") back
in 2.6.33.

Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld 2022-02-24 23:04:56 +01:00
parent a3f9e8910e
commit 64276a9939
1 changed files with 13 additions and 16 deletions
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29
drivers/char/random.c
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@ -1661,22 +1661,25 @@ const struct file_operations urandom_fops = {
static int sysctl_random_min_urandom_seed = 60; static int sysctl_random_min_urandom_seed = 60;
static int sysctl_random_write_wakeup_bits = POOL_MIN_BITS; static int sysctl_random_write_wakeup_bits = POOL_MIN_BITS;
static int sysctl_poolsize = POOL_BITS; static int sysctl_poolsize = POOL_BITS;
static char sysctl_bootid[16]; static u8 sysctl_bootid[UUID_SIZE];
/* /*
* This function is used to return both the bootid UUID, and random * This function is used to return both the bootid UUID, and random
* UUID. The difference is in whether table->data is NULL; if it is, * UUID. The difference is in whether table->data is NULL; if it is,
* then a new UUID is generated and returned to the user. * then a new UUID is generated and returned to the user.
*
* If the user accesses this via the proc interface, the UUID will be
* returned as an ASCII string in the standard UUID format; if via the
* sysctl system call, as 16 bytes of binary data.
*/ */
static int proc_do_uuid(struct ctl_table *table, int write, void *buffer, static int proc_do_uuid(struct ctl_table *table, int write, void *buffer,
size_t *lenp, loff_t *ppos) size_t *lenp, loff_t *ppos)
{ {
struct ctl_table fake_table; u8 tmp_uuid[UUID_SIZE], *uuid;
unsigned char buf[64], tmp_uuid[16], *uuid; char uuid_string[UUID_STRING_LEN + 1];
struct ctl_table fake_table = {
.data = uuid_string,
.maxlen = UUID_STRING_LEN
};
if (write)
return -EPERM;
uuid = table->data; uuid = table->data;
if (!uuid) { if (!uuid) {
@ -1691,12 +1694,8 @@ static int proc_do_uuid(struct ctl_table *table, int write, void *buffer,
spin_unlock(&bootid_spinlock); spin_unlock(&bootid_spinlock);
} }
sprintf(buf, "%pU", uuid); snprintf(uuid_string, sizeof(uuid_string), "%pU", uuid);
return proc_dostring(&fake_table, 0, buffer, lenp, ppos);
fake_table.data = buf;
fake_table.maxlen = sizeof(buf);
return proc_dostring(&fake_table, write, buffer, lenp, ppos);
} }
static struct ctl_table random_table[] = { static struct ctl_table random_table[] = {
@ -1731,13 +1730,11 @@ static struct ctl_table random_table[] = {
{ {
.procname = "boot_id", .procname = "boot_id",
.data = &sysctl_bootid, .data = &sysctl_bootid,
.maxlen = 16,
.mode = 0444, .mode = 0444,
.proc_handler = proc_do_uuid, .proc_handler = proc_do_uuid,
}, },
{ {
.procname = "uuid", .procname = "uuid",
.maxlen = 16,
.mode = 0444, .mode = 0444,
.proc_handler = proc_do_uuid, .proc_handler = proc_do_uuid,
}, },