2024-03-19 21:20:12

by Justin Stitt

Subject: [PATCH v3] soc: qcom: cmd-db: replace deprecated strncpy with strtomem

strncpy() is an ambiguous and potentially dangerous interface [1]. We
should prefer more robust and less ambiguous alternatives.

@query is marked as __nonstring and doesn't need to be NUL-terminated.

Since we are doing a string to memory copy, we can use the aptly named
"strtomem" -- specifically, the "pad" variant to also ensure NUL-padding
throughout the destination buffer.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: [email protected]
Reviewed-by: Kees Cook <[email protected]>
Signed-off-by: Justin Stitt <[email protected]>
---
Changes in v3:
- Prefer strtomem_pad (thanks Bjorn)
- Reword commit message (thanks Bjorn)
- Carry over Kees' RB as this new version is functionally the same and
matches the same spirit of v2
- Link to v2: https://lore.kernel.org/r/20240318-strncpy-drivers-soc-qcom-cmd-db-c-v2-1-8f6ebf1bd891@google.com

Changes in v2:
- use strtomem instead of memcpy (thanks Kees)
- Link to v1: https://lore.kernel.org/r/20240314-strncpy-drivers-soc-qcom-cmd-db-c-v1-1-70f5d5e70732@google.com
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
drivers/soc/qcom/cmd-db.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c
index a5fd68411bed..d51ae99d9c02 100644
--- a/drivers/soc/qcom/cmd-db.c
+++ b/drivers/soc/qcom/cmd-db.c
@@ -147,12 +147,7 @@ static int cmd_db_get_header(const char *id, const struct entry_header **eh,
if (ret)
return ret;

- /*
- * Pad out query string to same length as in DB. NOTE: the output
- * query string is not necessarily '\0' terminated if it bumps up
- * against the max size. That's OK and expected.
- */
- strncpy(query, id, sizeof(query));
+ strtomem_pad(query, id, 0);

for (i = 0; i < MAX_SLV_ID; i++) {
rsc_hdr = &cmd_db_header->header[i];

---
base-commit: fe46a7dd189e25604716c03576d05ac8a5209743
change-id: 20240314-strncpy-drivers-soc-qcom-cmd-db-c-284f3abaabb8

Best regards,
--
Justin Stitt <[email protected]>

2024-04-21 22:30:33

by Bjorn Andersson

Subject: Re: [PATCH v3] soc: qcom: cmd-db: replace deprecated strncpy with strtomem

On Tue, 19 Mar 2024 21:19:59 +0000, Justin Stitt wrote:
> strncpy() is an ambiguous and potentially dangerous interface [1]. We
> should prefer more robust and less ambiguous alternatives.
>
> @query is marked as __nonstring and doesn't need to be NUL-terminated.
>
> Since we are doing a string to memory copy, we can use the aptly named
> "strtomem" -- specifically, the "pad" variant to also ensure NUL-padding
> throughout the destination buffer.
>
> [...]

Applied, thanks!

[1/1] soc: qcom: cmd-db: replace deprecated strncpy with strtomem
commit: 166db01007ea802ff9933ac73ec8f140ca0cf5d5

Best regards,
--
Bjorn Andersson <[email protected]>