3.2-stable review patch. If anyone has any objections, please let me know.
------------------ From: Mathieu Desnoyers <[email protected]> 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 <[email protected]> Cc: "Theodore Ts'o" <[email protected]> Cc: Matt Mackall <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Ben Hutchings <[email protected]> --- drivers/char/random.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 54ca8b2..4ec04a7 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1260,10 +1260,15 @@ 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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
