From 8887c7d778dce8cadee422de97e557a224555bdf Mon Sep 17 00:00:00 2001 From: Tim Chase Date: Sun, 10 Jul 2016 09:09:02 -0500 Subject: Prevent null dereferences when accessing dbuf kstat In arc_buf_info(), the arc_buf_t may have no header. If not, don't try to fetch the arc buffer stats and instead just zero them. The null dereferences were observed while accessing the dbuf kstat with awk on a system in which millions of small files were being created in order to overflow the system's metadata limit. Signed-off-by: Tim Chase Signed-off-by: Brian Behlendorf Signed-off-by: Chunwei Chen Closes #4837 --- module/zfs/arc.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) (limited to 'module/zfs') diff --git a/module/zfs/arc.c b/module/zfs/arc.c index 77181b1fd..2dbca8da9 100644 --- a/module/zfs/arc.c +++ b/module/zfs/arc.c @@ -1461,6 +1461,13 @@ arc_buf_info(arc_buf_t *ab, arc_buf_info_t *abi, int state_index) l2arc_buf_hdr_t *l2hdr = NULL; arc_state_t *state = NULL; + memset(abi, 0, sizeof (arc_buf_info_t)); + + if (hdr == NULL) + return; + + abi->abi_flags = hdr->b_flags; + if (HDR_HAS_L1HDR(hdr)) { l1hdr = &hdr->b_l1hdr; state = l1hdr->b_state; @@ -1468,9 +1475,6 @@ arc_buf_info(arc_buf_t *ab, arc_buf_info_t *abi, int state_index) if (HDR_HAS_L2HDR(hdr)) l2hdr = &hdr->b_l2hdr; - memset(abi, 0, sizeof (arc_buf_info_t)); - abi->abi_flags = hdr->b_flags; - if (l1hdr) { abi->abi_datacnt = l1hdr->b_datacnt; abi->abi_access = l1hdr->b_arc_access; -- cgit v1.2.3