From d88a0240ff76062eb0728963e7aacf6dbe87f7c7 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 21 Sep 2022 13:51:55 -0700 Subject: scsi: scsi_transport_fc: Adjust struct fc_nl_event flex array usage In order to help the compiler reason about the destination buffer in struct fc_nl_event, add a flexible array member for this purpose. However, since the header is UAPI, it must not change size or layout, so a union is used. The allocation size calculations are also corrected (it was potentially allocating an extra 8 bytes), and the padding is zeroed to avoid leaking kernel heap memory contents. Detected at run-time by the recently added memcpy() bounds checking: memcpy: detected field-spanning write (size 8) of single field "&event->event_data" at drivers/scsi/scsi_transport_fc.c:581 (size 4) Link: https://lore.kernel.org/linux-next/42404B5E-198B-4FD3-94D6-5E16CF579EF3@linux.ibm.com/ Link: https://lore.kernel.org/r/20220921205155.1451649-1-keescook@chromium.org Cc: "James E.J. Bottomley" Cc: "Martin K. Petersen" Cc: linux-scsi@vger.kernel.org Reported-by: Sachin Sant Tested-by: Sachin Sant Reviewed-by: James Smart Signed-off-by: Kees Cook Signed-off-by: Martin K. Petersen --- drivers/scsi/scsi_transport_fc.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'drivers/scsi') diff --git a/drivers/scsi/scsi_transport_fc.c b/drivers/scsi/scsi_transport_fc.c index df4aa4a5f83c..8934160c4a33 100644 --- a/drivers/scsi/scsi_transport_fc.c +++ b/drivers/scsi/scsi_transport_fc.c @@ -543,7 +543,7 @@ fc_host_post_fc_event(struct Scsi_Host *shost, u32 event_number, struct nlmsghdr *nlh; struct fc_nl_event *event; const char *name; - u32 len; + size_t len, padding; int err; if (!data_buf || data_len < 4) @@ -554,7 +554,7 @@ fc_host_post_fc_event(struct Scsi_Host *shost, u32 event_number, goto send_fail; } - len = FC_NL_MSGALIGN(sizeof(*event) + data_len); + len = FC_NL_MSGALIGN(sizeof(*event) - sizeof(event->event_data) + data_len); skb = nlmsg_new(len, GFP_KERNEL); if (!skb) { @@ -578,7 +578,9 @@ fc_host_post_fc_event(struct Scsi_Host *shost, u32 event_number, event->event_num = event_number; event->event_code = event_code; if (data_len) - memcpy(&event->event_data, data_buf, data_len); + memcpy(event->event_data_flex, data_buf, data_len); + padding = len - offsetof(typeof(*event), event_data_flex) - data_len; + memset(event->event_data_flex + data_len, 0, padding); nlmsg_multicast(scsi_nl_sock, skb, 0, SCSI_NL_GRP_FC_EVENTS, GFP_KERNEL); -- cgit v1.2.3