Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 44e4360f authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Linus Torvalds
Browse files

drivers/char/random.c: fix boot id uniqueness race 



/proc/sys/kernel/random/boot_id can be read concurrently by userspace
processes.  If two (or more) user-space processes concurrently read
boot_id when sysctl_bootid is not yet assigned, a race can occur making
boot_id differ between the reads.  Because the whole point of the boot id
is to be unique across a kernel execution, fix this by protecting this
operation with a spinlock.

Given that this operation is not frequently used, hitting the spinlock
on each call should not be an issue.

Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d833049b

drivers/char/random.c

+8 −3
Original line number Original line Diff line number Diff line
@@ -1260,10 +1260,15 @@ static int proc_do_uuid(ctl_table *table, int write, 
	uuid = table->data;

	uuid = table->data;

	if (!uuid) {

	if (!uuid) {

		uuid = tmp_uuid;

		uuid = tmp_uuid;

		uuid[8] = 0;

	}

	if (uuid[8] == 0)

		generate_random_uuid(uuid);

		generate_random_uuid(uuid);

	} else {

		static DEFINE_SPINLOCK(bootid_spinlock);



		spin_lock(&bootid_spinlock);

		if (!uuid[8])

			generate_random_uuid(uuid);

		spin_unlock(&bootid_spinlock);

	}





	sprintf(buf, "%pU", uuid);

	sprintf(buf, "%pU", uuid);