* [PATCH] scsi: advansys: Prefer struct_size over open coded arithmetic
@ 2021-09-18 11:18 Len Baker
2021-09-20 23:57 ` Gustavo A. R. Silva
0 siblings, 1 reply; 2+ messages in thread
From: Len Baker @ 2021-09-18 11:18 UTC (permalink / raw)
To: Matthew Wilcox, Hannes Reinecke, James E.J. Bottomley,
Martin K. Petersen
Cc: Len Baker, Gustavo A. R. Silva, Kees Cook, linux-hardening,
linux-scsi, linux-kernel
As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.
So, refactor the code a bit to use the struct_size() helper instead of
the argument "size + count * size" in the kzalloc() function.
[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
Signed-off-by: Len Baker <len.baker@gmx.com>
---
drivers/scsi/advansys.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/advansys.c b/drivers/scsi/advansys.c
index ffb391967573..fe882502e7bf 100644
--- a/drivers/scsi/advansys.c
+++ b/drivers/scsi/advansys.c
@@ -7465,6 +7465,7 @@ static int asc_build_req(struct asc_board *boardp, struct scsi_cmnd *scp,
return ASC_BUSY;
} else if (use_sg > 0) {
int sgcnt;
+ size_t size;
struct scatterlist *slp;
struct asc_sg_head *asc_sg_head;
@@ -7477,8 +7478,8 @@ static int asc_build_req(struct asc_board *boardp, struct scsi_cmnd *scp,
return ASC_ERROR;
}
- asc_sg_head = kzalloc(sizeof(asc_scsi_q->sg_head) +
- use_sg * sizeof(struct asc_sg_list), GFP_ATOMIC);
+ size = struct_size(asc_scsi_q->sg_head, sg_list, use_sg);
+ asc_sg_head = kzalloc(size, GFP_ATOMIC);
if (!asc_sg_head) {
scsi_dma_unmap(scp);
set_host_byte(scp, DID_SOFT_ERROR);
--
2.25.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] scsi: advansys: Prefer struct_size over open coded arithmetic
2021-09-18 11:18 [PATCH] scsi: advansys: Prefer struct_size over open coded arithmetic Len Baker
@ 2021-09-20 23:57 ` Gustavo A. R. Silva
0 siblings, 0 replies; 2+ messages in thread
From: Gustavo A. R. Silva @ 2021-09-20 23:57 UTC (permalink / raw)
To: Len Baker, Matthew Wilcox, Hannes Reinecke, James E.J. Bottomley,
Martin K. Petersen
Cc: Gustavo A. R. Silva, Kees Cook, linux-hardening, linux-scsi,
linux-kernel
On 9/18/21 06:18, Len Baker wrote:
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
>
> So, refactor the code a bit to use the struct_size() helper instead of
> the argument "size + count * size" in the kzalloc() function.
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>
> Signed-off-by: Len Baker <len.baker@gmx.com>
> ---
> drivers/scsi/advansys.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/advansys.c b/drivers/scsi/advansys.c
> index ffb391967573..fe882502e7bf 100644
> --- a/drivers/scsi/advansys.c
> +++ b/drivers/scsi/advansys.c
> @@ -7465,6 +7465,7 @@ static int asc_build_req(struct asc_board *boardp, struct scsi_cmnd *scp,
> return ASC_BUSY;
> } else if (use_sg > 0) {
> int sgcnt;
> + size_t size;
I don't think a new variable is needed.
> struct scatterlist *slp;
> struct asc_sg_head *asc_sg_head;
>
> @@ -7477,8 +7478,8 @@ static int asc_build_req(struct asc_board *boardp, struct scsi_cmnd *scp,
> return ASC_ERROR;
> }
>
> - asc_sg_head = kzalloc(sizeof(asc_scsi_q->sg_head) +
> - use_sg * sizeof(struct asc_sg_list), GFP_ATOMIC);
> + size = struct_size(asc_scsi_q->sg_head, sg_list, use_sg);
> + asc_sg_head = kzalloc(size, GFP_ATOMIC);
You can go with this:
diff --git a/drivers/scsi/advansys.c b/drivers/scsi/advansys.c
index ffb391967573..e341b3372482 100644
--- a/drivers/scsi/advansys.c
+++ b/drivers/scsi/advansys.c
@@ -7477,8 +7477,8 @@ static int asc_build_req(struct asc_board *boardp, struct scsi_cmnd *scp,
return ASC_ERROR;
}
- asc_sg_head = kzalloc(sizeof(asc_scsi_q->sg_head) +
- use_sg * sizeof(struct asc_sg_list), GFP_ATOMIC);
+ asc_sg_head = kzalloc(struct_size(asc_sg_head, sg_list, use_sg),
+ GFP_ATOMIC);
if (!asc_sg_head) {
scsi_dma_unmap(scp);
set_host_byte(scp, DID_SOFT_ERROR);
It perfectly fits withing the 80 columns, which by the way is deprecated
but still good-to-have.
Also, if you are finding these instances with the help of Coccinelle, it'd be nice
if you mention that in the changelog text. :)
Thanks!
--
Gustavo
> if (!asc_sg_head) {
> scsi_dma_unmap(scp);
> set_host_byte(scp, DID_SOFT_ERROR);
> --
> 2.25.1
>
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2021-09-20 23:57 ` Gustavo A. R. Silva
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