[PATCH] md: fix a use-after-free bug in raid1

Who would submit code with a FIXME like that in it !!!!
Signed-off-by: NNeil Brown <neilb@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

drivers/md/raid1.c

@@ -320,7 +320,6 @@ static int raid1_end_write_request(struct bio *bio, unsigned int bytes_done, int
 		 * this branch is our 'one mirror IO has finished' event handler:
 		 */
 		r1_bio->bios[mirror] = NULL;
-		bio_put(bio);
 		if (!uptodate) {
 			md_error(r1_bio->mddev, conf->mirrors[mirror].rdev);
 			/* an I/O failed, we can't clear the bitmap */
@@ -377,7 +376,6 @@ static int raid1_end_write_request(struct bio *bio, unsigned int bytes_done, int
 		}
 		if (test_bit(R1BIO_BehindIO, &r1_bio->state)) {
 			/* free extra copy of the data pages */
-/* FIXME bio has been freed!!! */
 			int i = bio->bi_vcnt;
 			while (i--)
 				__free_page(bio->bi_io_vec[i].bv_page);
@@ -391,6 +389,9 @@ static int raid1_end_write_request(struct bio *bio, unsigned int bytes_done, int
 		raid_end_bio_io(r1_bio);
 	}
 
+	if (r1_bio->bios[mirror]==NULL)
+		bio_put(bio);
+
 	rdev_dec_pending(conf->mirrors[mirror].rdev, conf->mddev);
 	return 0;
 }