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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" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
Reported-by: Sachin Sant <sachinp@linux.ibm.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Reviewed-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Kees Cook 2022-09-21 13:51:55 -07:00 committed by Martin K. Petersen
parent 1a2433b0ec
commit d88a0240ff
2 changed files with 10 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
drivers/scsi/scsi_transport_fc.c
View File

@ -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);

7
include/uapi/scsi/scsi_netlink_fc.h
View File

@ -35,7 +35,7 @@
* FC Transport Broadcast Event Message :
* FC_NL_ASYNC_EVENT
*
* Note: if Vendor Unique message, &event_data will be start of
* Note: if Vendor Unique message, event_data_flex will be start of
* vendor unique payload, and the length of the payload is
* per event_datalen
*
@ -50,7 +50,10 @@ struct fc_nl_event {
__u16 event_datalen;
__u32 event_num;
__u32 event_code;
__u32 event_data;
union {
__u32 event_data;
__DECLARE_FLEX_ARRAY(__u8, event_data_flex);
};
} __attribute__((aligned(sizeof(__u64))));