From 9f00f9cf2be293efe899db67dc5272e3a9c62717 Mon Sep 17 00:00:00 2001 From: Xiang Mei Date: Mon, 8 Jun 2026 21:40:09 -0700 Subject: [PATCH] libceph: bound pg_{temp,upmap,upmap_items} length to CEPH_PG_MAX_SIZE __decode_pg_temp() decodes an user-controlled length but only rejects values large enough to overflow the allocation; it does not bound it to CEPH_PG_MAX_SIZE. The helper backs both pg_temp and pg_upmap decoding, and apply_upmap()/get_temp_osds() later copy the decoded list into the fixed-size on-stack array struct ceph_osds.osds[CEPH_PG_MAX_SIZE]. A monitor that sends an OSDMap with a pg_temp/pg_upmap entry longer than 32 thus causes a stack out-of-bounds write. An OSD set for a single PG can never exceed CEPH_PG_MAX_SIZE, so reject longer entries at decode time. The bound is well below the old overflow threshold, so it also covers the allocation-size overflow the previous check guarded against. BUG: KASAN: stack-out-of-bounds in ceph_pg_to_up_acting_osds Write of size 4 ... by task exploit kasan_report (mm/kasan/report.c:595) ceph_pg_to_up_acting_osds (net/ceph/osdmap.c:2617 net/ceph/osdmap.c:2833) calc_target (net/ceph/osd_client.c:1638) __submit_request (net/ceph/osd_client.c:2394) ceph_osdc_start_request (net/ceph/osd_client.c:2490) ceph_osdc_call (net/ceph/osd_client.c:5164) rbd_dev_image_probe (drivers/block/rbd.c:6899) do_rbd_add (drivers/block/rbd.c:7138) ... kernel BUG at net/ceph/osdmap.c:2670! [ idryomov: do the same in __decode_pg_upmap_items() ] Cc: stable@vger.kernel.org Fixes: a303bb0e5834 ("libceph: introduce and switch to decode_pg_mapping()") Reported-by: Weiming Shi Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Xiang Mei Reviewed-by: Alex Markuze Signed-off-by: Ilya Dryomov --- net/ceph/osdmap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c index 04036c047b8c..a4b0dd8672ec 100644 --- a/net/ceph/osdmap.c +++ b/net/ceph/osdmap.c @@ -1438,7 +1438,7 @@ static struct ceph_pg_mapping *__decode_pg_temp(void **p, void *end, ceph_decode_32_safe(p, end, len, e_inval); if (len == 0 && incremental) return NULL; /* new_pg_temp: [] to remove */ - if ((size_t)len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32)) + if (len > CEPH_PG_MAX_SIZE) return ERR_PTR(-EINVAL); ceph_decode_need(p, end, len * sizeof(u32), e_inval); @@ -1619,7 +1619,7 @@ static struct ceph_pg_mapping *__decode_pg_upmap_items(void **p, void *end, u32 len, i; ceph_decode_32_safe(p, end, len, e_inval); - if ((size_t)len > (SIZE_MAX - sizeof(*pg)) / (2 * sizeof(u32))) + if (len > CEPH_PG_MAX_SIZE) return ERR_PTR(-EINVAL); ceph_decode_need(p, end, 2 * len * sizeof(u32), e_inval);