From 3790689fa3c771bba6bafb7dee3e8389dd0b55bc Mon Sep 17 00:00:00 2001 From: Lachlan McIlroy Date: Wed, 13 Aug 2008 15:42:10 +1000 Subject: [PATCH] [XFS] Do not access buffers after dropping reference count We should not access a buffer after dropping it's reference count otherwise we could race with another thread that releases the final reference count and frees the buffer causing us to access potentially unmapped memory. The bug this change fixes only occured on DEBUG XFS since the offending code was in an ASSERT. SGI-PV: 984429 SGI-Modid: xfs-linux-melb:xfs-kern:31715a Signed-off-by: Lachlan McIlroy Signed-off-by: David Chinner --- fs/xfs/linux-2.6/xfs_buf.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c index 9cc8f02130..9f45c74f1a 100644 --- a/fs/xfs/linux-2.6/xfs_buf.c +++ b/fs/xfs/linux-2.6/xfs_buf.c @@ -838,6 +838,7 @@ xfs_buf_rele( return; } + ASSERT(atomic_read(&bp->b_hold) > 0); if (atomic_dec_and_lock(&bp->b_hold, &hash->bh_lock)) { if (bp->b_relse) { atomic_inc(&bp->b_hold); @@ -851,11 +852,6 @@ xfs_buf_rele( spin_unlock(&hash->bh_lock); xfs_buf_free(bp); } - } else { - /* - * Catch reference count leaks - */ - ASSERT(atomic_read(&bp->b_hold) >= 0); } } -- 2.39.5