| Date | Tue, 02 Oct 2012 00:54:43 +0200 | From | Willy Tarreau <> | Subject | [ 166/180] drivers/char/random.c: fix boot id uniqueness race |
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2.6.32-longterm review patch. If anyone has any objections, please let me know.
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From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Willy Tarreau <w@1wt.eu> --- 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 5e106b1..0c38849 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1258,10 +1258,15 @@ 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, "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-" "%02x%02x%02x%02x%02x%02x", -- 1.7.2.1.45.g54fbc
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