diff options
| author | Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | 2012-04-12 12:49:12 -0700 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2012-09-12 03:37:29 +0100 |
| commit | a457fb130726356e758eeadf230b21993986d0ab (patch) | |
| tree | 5cc2073b0629755ab4dd51d9d435b7a5e40f4046 | |
| parent | 39b78b60059ba51c89008f93139719b489639124 (diff) | |
drivers/char/random.c: fix boot id uniqueness race
commit 44e4360fa3384850d65dd36fb4e6e5f2f112709b upstream.
/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: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | drivers/char/random.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 631d4f6728f3..918979fb4131 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1391,10 +1391,15 @@ static int proc_do_uuid(ctl_table *table, int write, uuid = table->data; if (!uuid) { uuid = tmp_uuid; - uuid[8] = 0; - } - if (uuid[8] == 0) 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); |