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Subject[PATCH] random: cleanup UUID handling
Date
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.

Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
drivers/char/random.c | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 1d6cb0779acd..a26c6e7cc93b 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1632,11 +1632,11 @@ const struct file_operations urandom_fops = {
static int sysctl_random_min_urandom_seed = 60;
static int sysctl_random_write_wakeup_bits = POOL_MIN_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
- * 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.
*
* If the user accesses this via the proc interface, the UUID will be
@@ -1646,8 +1646,15 @@ static char sysctl_bootid[16];
static int proc_do_uuid(struct ctl_table *table, int write, void *buffer,
size_t *lenp, loff_t *ppos)
{
- struct ctl_table fake_table;
- unsigned char buf[64], tmp_uuid[16], *uuid;
+ u8 tmp_uuid[UUID_SIZE], *uuid;
+ char uuid_string[UUID_STRING_LEN + 1];
+ struct ctl_table fake_table = {
+ .data = uuid_string,
+ .maxlen = sizeof(uuid_string)
+ };
+
+ if (write)
+ return -EPERM;

uuid = table->data;
if (!uuid) {
@@ -1662,12 +1669,8 @@ static int proc_do_uuid(struct ctl_table *table, int write, void *buffer,
spin_unlock(&bootid_spinlock);
}

- sprintf(buf, "%pU", uuid);
-
- fake_table.data = buf;
- fake_table.maxlen = sizeof(buf);
-
- return proc_dostring(&fake_table, write, buffer, lenp, ppos);
+ snprintf(uuid_string, sizeof(uuid_string), "%pU", uuid);
+ return proc_dostring(&fake_table, 0, buffer, lenp, ppos);
}

static struct ctl_table random_table[] = {
@@ -1702,13 +1705,11 @@ static struct ctl_table random_table[] = {
{
.procname = "boot_id",
.data = &sysctl_bootid,
- .maxlen = 16,
.mode = 0444,
.proc_handler = proc_do_uuid,
},
{
.procname = "uuid",
- .maxlen = 16,
.mode = 0444,
.proc_handler = proc_do_uuid,
},
--
2.35.1
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