gfs2: Add missing else in trans_add_meta/data

PATCH New Bob Peterson 1 participant 1 message Oct 1, 2015 1 message not in the archive GFS2 file system

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Bob Peterson

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2015-10-01 17:00 UTC #1 lore raw

PATCH 1/1 gfs2: Add missing else in trans_add_meta/data

Hi,

This patch fixes a timing window that causes a segfault. The problem is that bd can remain NULL throughout the function and then reference that NULL pointer if the bh->b_private starts out NULL, then someone sets it to non-NULL inside the locking. In that case, bd still needs to be set.

Regards,

Bob Peterson
Red Hat File Systems

Signed-off-by Bob Peterson <[email protected]>

---
 fs/gfs2/trans.c | 4 ++++
 1 file changed, 4 insertions(+)

fs/gfs2/trans.c +4 -0

index b95d0d6..0c1bde3 100644
@@ -176,6 +176,8 @@ void gfs2_trans_add_data(struct gfs2_glock *gl, struct buffer_head *bh)
 		unlock_buffer(bh);
 		if (bh->b_private == NULL)
 			bd = gfs2_alloc_bufdata(gl, bh, &gfs2_databuf_lops);
+		else
+			bd = bh->b_private;
 		lock_buffer(bh);
 		gfs2_log_lock(sdp);
 	}

@@ -236,6 +238,8 @@ void gfs2_trans_add_meta(struct gfs2_glock *gl, struct buffer_head *bh)
 		lock_page(bh->b_page);
 		if (bh->b_private == NULL)
 			bd = gfs2_alloc_bufdata(gl, bh, &gfs2_buf_lops);
+		else
+			bd = bh->b_private;
 		unlock_page(bh->b_page);
 		lock_buffer(bh);
 		gfs2_log_lock(sdp);