random: cleanup UUID handling
commit 64276a9939ff414f2f0db38036cf4e1a0a703394 upstream.
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
894d2491153a ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 1a4e3ee..3b14ae9 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1655,22 +1655,25 @@
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
- * 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 __user *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 = UUID_STRING_LEN
+ };
+
+ if (write)
+ return -EPERM;
uuid = table->data;
if (!uuid) {
@@ -1685,12 +1688,8 @@
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);
}
extern struct ctl_table random_table[];
@@ -1726,13 +1725,11 @@
{
.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,
},
diff --git a/include/linux/uuid.h b/include/linux/uuid.h
index 2d095fc..c77fb14 100644
--- a/include/linux/uuid.h
+++ b/include/linux/uuid.h
@@ -23,6 +23,7 @@
* not including trailing NUL.
*/
#define UUID_STRING_LEN 36
+#define UUID_SIZE 16
static inline int uuid_le_cmp(const uuid_le u1, const uuid_le u2)
{