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| author | Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | 2012-04-12 12:49:12 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-04-12 13:12:12 -0700 |
| commit | 44e4360fa3384850d65dd36fb4e6e5f2f112709b (patch) | |
| tree | bca5390346511ef308933b9968cdc43ec8569b7f /drivers/char | |
| parent | d833049bd20570cbbadeb5228c579f9f3aaa4e03 (diff) | |
| download | linux-44e4360fa3384850d65dd36fb4e6e5f2f112709b.tar.gz | |
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: 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>
Diffstat (limited to 'drivers/char')
| -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 54ca8b23cde3..4ec04a754733 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); |