Re: linux-next: build failure after merge of the kspp tree

Kees Cook
2022-01-25T06:16:26Z

On Tue, Jan 25, 2022 at 02:24:30PM +1100, Stephen Rothwell wrote:
> Hi all,
>
> After merging the kspp tree, today's linux-next build (powerpc
> allyesconfig) failed like this:
>
>
> drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c: In function 'ibmvscsis_send_messages':
> drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c:1934:44: error: array subscript 'struct viosrp_crq[0]' is partly outside array bounds of 'u64[1]' {aka 'long long unsigned int[1]'} [-Werror=array-bounds]
> 1934 | crq->valid = VALID_CMD_RESP_EL;
> | ^~
> drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c:1875:13: note: while referencing 'msg_hi'
> 1875 | u64 msg_hi = 0;
> | ^~~~~~
> drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c:1935:44: error: array subscript 'struct viosrp_crq[0]' is partly outside array bounds of 'u64[1]' {aka 'long long unsigned int[1]'} [-Werror=array-bounds]
> 1935 | crq->format = cmd->rsp.format;
> | ^~
> drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c:1875:13: note: while referencing 'msg_hi'
> 1875 | u64 msg_hi = 0;
> | ^~~~~~
> drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c:1938:52: error: array subscript 'struct viosrp_crq[0]' is partly outside array bounds of 'u64[1]' {aka 'long long unsigned int[1]'} [-Werror=array-bounds]
> 1938 | crq->status = VIOSRP_ADAPTER_FAIL;
> | ^~
> drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c:1875:13: note: while referencing 'msg_hi'
> 1875 | u64 msg_hi = 0;
> | ^~~~~~
> drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c:1940:44: error: array subscript 'struct viosrp_crq[0]' is partly outside array bounds of 'u64[1]' {aka 'long long unsigned int[1]'} [-Werror=array-bounds]
> 1940 | crq->IU_length = cpu_to_be16(cmd->rsp.len);
> | ^~
> drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c:1875:13: note: while referencing 'msg_hi'
> 1875 | u64 msg_hi = 0;
> | ^~~~~~
>
> Exposed by commit
>
> 4ba545781e20 ("Makefile: Enable -Warray-bounds")
>
> Probably introduced by commit
>
> 88a678bbc34c ("ibmvscsis: Initial commit of IBM VSCSI Tgt Driver")
>
> I applied the following hack for now:
>
> From: Stephen Rothwell <sfr@canb.auug.org.au>
> Date: Tue, 25 Jan 2022 14:18:36 +1100
> Subject: [PATCH] scsi: hack for building with -Warray-bounds
>
> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
> ---
> drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c b/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c
> index 61f06f6885a5..89fcf98c61c3 100644
> --- a/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c
> +++ b/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c
> @@ -1872,11 +1872,11 @@ static void srp_snd_msg_failed(struct scsi_info *vscsi, long rc)
> */
> static void ibmvscsis_send_messages(struct scsi_info *vscsi)
> {
> - u64 msg_hi = 0;
> + u64 msg_hi[2] = { };
> /* note do not attempt to access the IU_data_ptr with this pointer
> * it is not valid
> */
> - struct viosrp_crq *crq = (struct viosrp_crq *)&msg_hi;
> + struct viosrp_crq *crq = (struct viosrp_crq *)msg_hi;
> struct ibmvscsis_cmd *cmd, *nxt;
> long rc = ADAPT_SUCCESS;
> bool retry = false;
> @@ -1940,7 +1940,7 @@ static void ibmvscsis_send_messages(struct scsi_info *vscsi)
> crq->IU_length = cpu_to_be16(cmd->rsp.len);
>
> rc = h_send_crq(vscsi->dma_dev->unit_address,
> - be64_to_cpu(msg_hi),
> + be64_to_cpu(msg_hi[0]),
> be64_to_cpu(cmd->rsp.tag));
>
> dev_dbg(&vscsi->dev, "send_messages: cmd %p, tag 0x%llx, rc %ld\n",

This looks correct to me. struct viosrp_crq is 16 bytes wide. The only
suggestion I might make would be either avoid the bare '2':

u64 msg_hi[sizeof(struct viosrp_crq) / sizeof(u64)] = { };

or adjust struct viosrp_crq so the casting isn't needed at all:

truct viosrp_crq {
union {
u64 hi;
struct {
u8 valid; /* used by RPA */
u8 format; /* SCSI vs out-of-band */
u8 reserved;
u8 status; /* non-scsi failure? (e.g. DMA failure) */
__be16 timeout; /* in seconds */
__be16 IU_length; /* in bytes */
};
};
__be64 IU_data_ptr; /* the TCE for transferring data */
};

struct viosrp_crq crq = { };
...
rc = h_send_crq(vscsi->dma_dev->unit_address,
be64_to_cpu(crq.hi),
be64_to_cpu(cmd->rsp.tag));

--
Kees Cook