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Message-ID: <202310161242.B0F9B693@keescook> Date: Mon, 16 Oct 2023 12:42:22 -0700 From: Kees Cook <keescook@...omium.org> To: Justin Stitt <justinstitt@...gle.com> Cc: Thomas Sailer <t.sailer@...mni.ethz.ch>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, linux-hams@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH v2] hamradio: replace deprecated strncpy with strscpy_pad On Mon, Oct 16, 2023 at 06:42:42PM +0000, Justin Stitt wrote: > strncpy() is deprecated for use on NUL-terminated destination strings > [1] and as such we should prefer more robust and less ambiguous string > interfaces. > > We expect both hi.data.modename and hi.data.drivername to be > NUL-terminated based on its usage with sprintf: > | sprintf(hi.data.modename, "%sclk,%smodem,fclk=%d,bps=%d%s", > | bc->cfg.intclk ? "int" : "ext", > | bc->cfg.extmodem ? "ext" : "int", bc->cfg.fclk, bc->cfg.bps, > | bc->cfg.loopback ? ",loopback" : ""); > > Note that this data is copied out to userspace with: > | if (copy_to_user(data, &hi, sizeof(hi))) > ... however, the data was also copied FROM the user here: > | if (copy_from_user(&hi, data, sizeof(hi))) > > Considering the above, a suitable replacement is strscpy_pad() as it > guarantees NUL-termination on the destination buffer while also > NUL-padding (which is good+wanted behavior when copying data to > userspace). > > 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> Thanks! Reviewed-by: Kees Cook <keescook@...omium.org> -- Kees Cook
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