ploop_pio_nr_segs() used for_each_bvec() to count the number of
segments in a pio. for_each_bvec() iterates via bvec_iter_bvec()
which clamps each segment to a single page boundary, so a single
multi-page bvec entry would be counted as multiple page-sized
segments. This overcounted nr_segs was then passed to iov_iter_bvec()
in ploop_submit_rw_mapped().
iov_iter_bvec_advance() uses nr_segs as the bvec array bound
(end = bvec + i->nr_segs), iterating one full bvec entry per step.
With an inflated nr_segs it reads past the end of the bvec array,
causing the KASAN slab-out-of-bounds in iov_iter_advance().
Fix by replacing for_each_bvec() with a manual loop that counts
actual bvec array entries, advancing through whole bvec entries
(respecting each entry's full bv_len) instead of page-sized
sub-segments.
Fixes: aceb22ce0b890 ("dm-ploop: Add ploop target driver")
https://virtuozzo.atlassian.net/browse/VSTOR-126957
Signed-off-by: Konstantin Khorenko <[email protected]>
Feature: dm-ploop: ploop target driver
---
v2 changes:
- a new macros has been introduced similar to the qcow2_for_each_bvec
to make the code closer to dm-qcow2 driver
---
drivers/md/dm-ploop-map.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index 2739cc3f09028..26224fcc8095d 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -34,6 +34,19 @@ static void ploop_prq_endio(struct pio *pio, void *prq_ptr,
extern struct static_key_false ploop_standby_check;
+/*
+ * Iterate over bvec entries without clamping to page boundaries.
+ * Unlike for_each_bvec() which uses bvec_iter_bvec() and splits
+ * multi-page entries into PAGE_SIZE chunks, this macro uses
+ * mp_bvec_iter_bvec() to walk actual bio_vec array entries.
+ */
+#define ploop_for_each_bvec(bv, bvec, iter, start) \
+ for (iter = start; \
+ iter.bi_size && \
+ ((bv = mp_bvec_iter_bvec(bvec, iter)), 1) && \
+ bv.bv_len; \
+ bvec_iter_advance(bvec, &iter, bv.bv_len))
+
static unsigned int ploop_pio_nr_segs(struct pio *pio)
{
struct bvec_iter bi = {
@@ -44,10 +57,10 @@ static unsigned int ploop_pio_nr_segs(struct pio *pio)
unsigned int nr_segs = 0;
struct bio_vec bv;
- for_each_bvec(bv, pio->bi_io_vec, bi, bi)
- nr_segs++;
+ ploop_for_each_bvec(bv, pio->bi_io_vec, bi, bi)
+ nr_segs++;
- return nr_segs;
+ return nr_segs;
}
static sector_t ploop_rq_pos(struct ploop *ploop, struct request *rq)
--
2.43.0
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