6.12-stable review patch. If anyone has any objections, please let me know.
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From: Hans de Goede hdegoede@redhat.com
commit 00f1cc14da0f06d2897b8c528df7c7dcf1b8da50 upstream.
gcc 15 honors the __counted_by(len) attribute on vsc_tp_packet.buf[] and the vsc-tp.c code is using this in a wrong way. len does not contain the available size in the buffer, it contains the actual packet length *without* the crc. So as soon as vsc_tp_xfer() tries to add the crc to buf[] the fortify-panic handler gets triggered:
[ 80.842193] memcpy: detected buffer overflow: 4 byte write of buffer size 0 [ 80.842243] WARNING: CPU: 4 PID: 272 at lib/string_helpers.c:1032 __fortify_report+0x45/0x50 ... [ 80.843175] __fortify_panic+0x9/0xb [ 80.843186] vsc_tp_xfer.cold+0x67/0x67 [mei_vsc_hw] [ 80.843210] ? seqcount_lockdep_reader_access.constprop.0+0x82/0x90 [ 80.843229] ? lockdep_hardirqs_on+0x7c/0x110 [ 80.843250] mei_vsc_hw_start+0x98/0x120 [mei_vsc] [ 80.843270] mei_reset+0x11d/0x420 [mei]
The easiest fix would be to just drop the counted-by but with the exception of the ack buffer in vsc_tp_xfer_helper() which only contains enough room for the packet-header, all other uses of vsc_tp_packet always use a buffer of VSC_TP_MAX_XFER_SIZE bytes for the packet.
Instead of just dropping the counted-by, split the vsc_tp_packet struct definition into a header and a full-packet definition and use a fixed size buf[] in the packet definition, this way fortify-source buffer overrun checking still works when enabled.
Fixes: 566f5ca97680 ("mei: Add transport driver for IVSC device") Cc: stable@kernel.org Signed-off-by: Hans de Goede hdegoede@redhat.com Reviewed-by: Alexander Usyskin alexander.usyskin@intel.com Reviewed-by: Sakari Ailus sakari.ailus@linux.intel.com Link: https://lore.kernel.org/r/20250318141203.94342-2-hdegoede@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/misc/mei/vsc-tp.c | 26 +++++++++++++++----------- 1 file changed, 15 insertions(+), 11 deletions(-)
--- a/drivers/misc/mei/vsc-tp.c +++ b/drivers/misc/mei/vsc-tp.c @@ -36,20 +36,24 @@ #define VSC_TP_XFER_TIMEOUT_BYTES 700 #define VSC_TP_PACKET_PADDING_SIZE 1 #define VSC_TP_PACKET_SIZE(pkt) \ - (sizeof(struct vsc_tp_packet) + le16_to_cpu((pkt)->len) + VSC_TP_CRC_SIZE) + (sizeof(struct vsc_tp_packet_hdr) + le16_to_cpu((pkt)->hdr.len) + VSC_TP_CRC_SIZE) #define VSC_TP_MAX_PACKET_SIZE \ - (sizeof(struct vsc_tp_packet) + VSC_TP_MAX_MSG_SIZE + VSC_TP_CRC_SIZE) + (sizeof(struct vsc_tp_packet_hdr) + VSC_TP_MAX_MSG_SIZE + VSC_TP_CRC_SIZE) #define VSC_TP_MAX_XFER_SIZE \ (VSC_TP_MAX_PACKET_SIZE + VSC_TP_XFER_TIMEOUT_BYTES) #define VSC_TP_NEXT_XFER_LEN(len, offset) \ - (len + sizeof(struct vsc_tp_packet) + VSC_TP_CRC_SIZE - offset + VSC_TP_PACKET_PADDING_SIZE) + (len + sizeof(struct vsc_tp_packet_hdr) + VSC_TP_CRC_SIZE - offset + VSC_TP_PACKET_PADDING_SIZE)
-struct vsc_tp_packet { +struct vsc_tp_packet_hdr { __u8 sync; __u8 cmd; __le16 len; __le32 seq; - __u8 buf[] __counted_by(len); +}; + +struct vsc_tp_packet { + struct vsc_tp_packet_hdr hdr; + __u8 buf[VSC_TP_MAX_XFER_SIZE - sizeof(struct vsc_tp_packet_hdr)]; };
struct vsc_tp { @@ -158,12 +162,12 @@ static int vsc_tp_dev_xfer(struct vsc_tp static int vsc_tp_xfer_helper(struct vsc_tp *tp, struct vsc_tp_packet *pkt, void *ibuf, u16 ilen) { - int ret, offset = 0, cpy_len, src_len, dst_len = sizeof(struct vsc_tp_packet); + int ret, offset = 0, cpy_len, src_len, dst_len = sizeof(struct vsc_tp_packet_hdr); int next_xfer_len = VSC_TP_PACKET_SIZE(pkt) + VSC_TP_XFER_TIMEOUT_BYTES; u8 *src, *crc_src, *rx_buf = tp->rx_buf; int count_down = VSC_TP_MAX_XFER_COUNT; u32 recv_crc = 0, crc = ~0; - struct vsc_tp_packet ack; + struct vsc_tp_packet_hdr ack; u8 *dst = (u8 *)&ack; bool synced = false;
@@ -280,10 +284,10 @@ int vsc_tp_xfer(struct vsc_tp *tp, u8 cm
guard(mutex)(&tp->mutex);
- pkt->sync = VSC_TP_PACKET_SYNC; - pkt->cmd = cmd; - pkt->len = cpu_to_le16(olen); - pkt->seq = cpu_to_le32(++tp->seq); + pkt->hdr.sync = VSC_TP_PACKET_SYNC; + pkt->hdr.cmd = cmd; + pkt->hdr.len = cpu_to_le16(olen); + pkt->hdr.seq = cpu_to_le32(++tp->seq); memcpy(pkt->buf, obuf, olen);
crc = ~crc32(~0, (u8 *)pkt, sizeof(pkt) + olen);