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authorPeter Hurley <peter@hurleysoftware.com>2016-01-09 22:55:36 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-01-27 16:41:04 -0800
commitfbaa122718a1235f4f83baa3abaad21cfefdbc9d (patch)
tree4ded90498dab94dce2f1c2c6679558ff217343fb /drivers/tty/tty_audit.c
parent5493090fc2341d9f28bdd9e81445fe0a130bafc2 (diff)
downloadlinux-fbaa122718a1235f4f83baa3abaad21cfefdbc9d.tar.bz2
tty: audit: Simplify first-use allocation
The first-use tty audit buffer allocation is a potential race amongst multiple attempts at 'first-use'; only one 'winner' is acceptable. The successful buffer assignment occurs if tty_audit_buf == NULL (which will also be the return from cmpxchg()); otherwise, another racer 'won' and this buffer allocation is freed. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/tty_audit.c')
-rw-r--r--drivers/tty/tty_audit.c22
1 files changed, 7 insertions, 15 deletions
diff --git a/drivers/tty/tty_audit.c b/drivers/tty/tty_audit.c
index 71ba8baee14d..6e33e41ec74d 100644
--- a/drivers/tty/tty_audit.c
+++ b/drivers/tty/tty_audit.c
@@ -181,30 +181,22 @@ int tty_audit_push(void)
*/
static struct tty_audit_buf *tty_audit_buf_get(void)
{
- struct tty_audit_buf *buf, *buf2;
- unsigned long flags;
+ struct tty_audit_buf *buf;
buf = current->signal->tty_audit_buf;
if (buf)
return buf;
- buf2 = tty_audit_buf_alloc();
- if (buf2 == NULL) {
+ buf = tty_audit_buf_alloc();
+ if (buf == NULL) {
audit_log_lost("out of memory in TTY auditing");
return NULL;
}
- spin_lock_irqsave(&current->sighand->siglock, flags);
- buf = current->signal->tty_audit_buf;
- if (!buf) {
- current->signal->tty_audit_buf = buf2;
- buf = buf2;
- buf2 = NULL;
- }
- spin_unlock_irqrestore(&current->sighand->siglock, flags);
- if (buf2)
- tty_audit_buf_free(buf2);
- return buf;
+ /* Race to use this buffer, free it if another wins */
+ if (cmpxchg(&current->signal->tty_audit_buf, NULL, buf) != NULL)
+ tty_audit_buf_free(buf);
+ return current->signal->tty_audit_buf;
}
/**