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Message-ID: <1cfc7c64-439c-437e-af82-7fce1202242d@quicinc.com> Date: Fri, 13 Oct 2023 17:58:03 -0700 From: Jeff Johnson <quic_jjohnson@...cinc.com> To: Justin Stitt <justinstitt@...gle.com>, Kalle Valo <kvalo@...nel.org> CC: <ath10k@...ts.infradead.org>, <linux-wireless@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <linux-hardening@...r.kernel.org> Subject: Re: [PATCH] ath10k: replace deprecated strncpy with strtomem_pad On 10/13/2023 1:33 PM, Justin Stitt wrote: > strncpy() is deprecated [1] and we should prefer less ambiguous > interfaces. > > In this case, arvif->u.ap.ssid has its length maintained by > arvif->u.ap.ssid_len which indicates it may not need to be > NUL-terminated, although by virtue of using strtomem_pad (with NUL-byte > pad character) and having a destination size larger than the source, > ssid will, incidentally, be NUL-terminated here. > > As strtomem_pad() docs say: > * @dest: Pointer of destination character array (marked as __nonstring) > * @src: Pointer to NUL-terminated string > * @pad: Padding character to fill any remaining bytes of @dest after copy > * > * This is a replacement for strncpy() uses where the destination is not > * a NUL-terminated string, but with bounds checking on the source size, and > * an explicit padding character. If padding is not required, use strtomem(). > > Let's also mark ath10k_vif.u.ap.ssid as __nonstring. what criteria is used to determine whether or not to use __nonstring? doesn't the use of u8 vs char already communicate that distinction? just want to know what other u8 arrays might require this. FWIW the documentation referenced by the __nonstring macro explicitly refers to "type array of char, signed char, or unsigned char" > > It is unclear to me whether padding is strictly necessary. Perhaps we > should opt for just strtomem() -- padding certainly doesn't hurt, > though. concur that padding probably isn't necessary but doesn't hurt, and will prevent confusion if looking at this member in a crashdump > > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] > Link: https://github.com/KSPP/linux/issues/90 > Cc: linux-hardening@...r.kernel.org > Signed-off-by: Justin Stitt <justinstitt@...gle.com> Either with or without the __nonstring... Acked-by: Jeff Johnson <quic_jjohnson@...cinc.com>
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