2023-08-09 02:08:41

by Justin Stitt

Subject: [PATCH v2 7/7] netfilter: xtables: refactor deprecated strncpy

Prefer `strscpy_pad` as it's a more robust interface whilst maintaing
zero-padding behavior.

There may have existed a bug here due to both `tbl->repl.name` and
`info->name` having a size of 32 as defined below:
| #define XT_TABLE_MAXNAMELEN 32

This may lead to buffer overreads in some situations -- `strscpy` solves
this by guaranteeing NUL-termination of the dest buffer.

Signed-off-by: Justin Stitt <[email protected]>

---
Note: build tested only
---
net/netfilter/xt_repldata.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/xt_repldata.h b/net/netfilter/xt_repldata.h
index 68ccbe50bb1e..5d1fb7018dba 100644
--- a/net/netfilter/xt_repldata.h
+++ b/net/netfilter/xt_repldata.h
@@ -29,7 +29,7 @@
if (tbl == NULL) \
return NULL; \
term = (struct type##_error *)&(((char *)tbl)[term_offset]); \
- strncpy(tbl->repl.name, info->name, sizeof(tbl->repl.name)); \
+ strscpy_pad(tbl->repl.name, info->name, sizeof(tbl->repl.name)); \
*term = (struct type##_error)typ2##_ERROR_INIT; \
tbl->repl.valid_hooks = hook_mask; \
tbl->repl.num_entries = nhooks + 1; \

--
2.41.0.640.ga95def55d0-goog

2023-08-09 20:45:32

by Florian Westphal

Subject: Re: [PATCH v2 7/7] netfilter: xtables: refactor deprecated strncpy

Justin Stitt <[email protected]> wrote:
> Prefer `strscpy_pad` as it's a more robust interface whilst maintaing
> zero-padding behavior.
>
> There may have existed a bug here due to both `tbl->repl.name` and
> `info->name` having a size of 32 as defined below:
> | #define XT_TABLE_MAXNAMELEN 32
>
> This may lead to buffer overreads in some situations -- `strscpy` solves
> this by guaranteeing NUL-termination of the dest buffer.

I don't think we need to use _pad here.