[PATCH net] net: marvell: prestera: use unaligned accessors for DSA tag
From: Runyu Xiao <hidden>
Date: 2026-06-20 09:42:58
Also in:
lkml, stable
Subsystem:
marvell prestera ethernet switch driver, networking drivers, the rest · Maintainers:
Elad Nachman, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Prestera parses and builds its 16-byte DSA tag from an skb byte buffer.
The current code casts the tag pointer to __be32 * and then reads or
writes the four tag words through that typed pointer.
The tag pointer is derived from skb data, but that only identifies the
protocol tag location inside the packet buffer. It does not make the tag
a naturally aligned __be32 array. Use the unaligned big-endian helpers
for both parsing and building the tag.
This issue was detected by our static analysis tool and confirmed by
manual audit. The same access pattern was validated with UBSAN alignment
instrumentation by keeping the original cast from a u8 DSA tag buffer to
__be32 * and reading dsa_words[i] from a deliberately misaligned tag
buffer. UBSAN reported misaligned-access loads of type '__be32' in
prestera_dsa_parse().
The driver has the same source-level issue: the RX path parses bytes at
skb->data - ETH_TLEN, and the TX path writes the tag at skb->data +
2 * ETH_ALEN. Those offsets identify the DSA tag bytes, but they do not
establish a __be32 object or a 4-byte alignment guarantee for typed loads
and stores.
Fixes: 501ef3066c89 ("net: marvell: prestera: Add driver for Prestera family ASIC devices")
Cc: stable@vger.kernel.org
Signed-off-by: Runyu Xiao <redacted>
---
.../ethernet/marvell/prestera/prestera_dsa.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/drivers/net/ethernet/marvell/prestera/prestera_dsa.c b/drivers/net/ethernet/marvell/prestera/prestera_dsa.c
index b7e89c0ca5c0..276f98cbd50e 100644
--- a/drivers/net/ethernet/marvell/prestera/prestera_dsa.c
+++ b/drivers/net/ethernet/marvell/prestera/prestera_dsa.c@@ -4,6 +4,7 @@ #include <linux/bitfield.h> #include <linux/bitops.h> #include <linux/errno.h> +#include <linux/unaligned.h> #include <linux/string.h> #include "prestera_dsa.h"
@@ -33,15 +34,14 @@ int prestera_dsa_parse(struct prestera_dsa *dsa, const u8 *dsa_buf) { - __be32 *dsa_words = (__be32 *)dsa_buf; enum prestera_dsa_cmd cmd; u32 words[4]; u32 field; - words[0] = ntohl(dsa_words[0]); - words[1] = ntohl(dsa_words[1]); - words[2] = ntohl(dsa_words[2]); - words[3] = ntohl(dsa_words[3]); + words[0] = get_unaligned_be32(dsa_buf); + words[1] = get_unaligned_be32(dsa_buf + 4); + words[2] = get_unaligned_be32(dsa_buf + 8); + words[3] = get_unaligned_be32(dsa_buf + 12); /* set the common parameters */ cmd = (enum prestera_dsa_cmd)FIELD_GET(PRESTERA_DSA_W0_CMD, words[0]);
@@ -82,7 +82,6 @@ int prestera_dsa_parse(struct prestera_dsa *dsa, const u8 *dsa_buf) int prestera_dsa_build(const struct prestera_dsa *dsa, u8 *dsa_buf) { - __be32 *dsa_words = (__be32 *)dsa_buf; u32 dev_num = dsa->hw_dev_num; u32 words[4] = { 0 };
@@ -98,10 +97,10 @@ int prestera_dsa_build(const struct prestera_dsa *dsa, u8 *dsa_buf) words[1] |= FIELD_PREP(PRESTERA_DSA_W1_EXT_BIT, 1); words[2] |= FIELD_PREP(PRESTERA_DSA_W2_EXT_BIT, 1); - dsa_words[0] = htonl(words[0]); - dsa_words[1] = htonl(words[1]); - dsa_words[2] = htonl(words[2]); - dsa_words[3] = htonl(words[3]); + put_unaligned_be32(words[0], dsa_buf); + put_unaligned_be32(words[1], dsa_buf + 4); + put_unaligned_be32(words[2], dsa_buf + 8); + put_unaligned_be32(words[3], dsa_buf + 12); return 0; }
--
2.34.1