Hi, On 9/6/23 16:09, Ingo Molnar wrote: > > * Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > >> Hi Ingo, >> >> On 9/6/23 14:10, Ingo Molnar wrote: >>> >>> * Justin Stitt <justinstitt@xxxxxxxxxx> wrote: >>> >>>> Both `strncpy` and `strcpy` are deprecated for use on NUL-terminated >>>> destination strings [1]. >>>> >>>> We can see that `arg` and `uv_nmi_action` are expected to be >>>> NUL-terminated strings due to their use within `strcmp()` and format >>>> strings respectively. >>>> >>>> With this in mind, a suitable replacement is `strscpy` [2] due to the >>>> fact that it guarantees NUL-termination on its destination buffer >>>> argument which is _not_ the case for `strncpy` or `strcpy`! >>>> >>>> In this case, we can drop both the forced NUL-termination and the `... -1` from: >>>> | strncpy(arg, val, ACTION_LEN - 1); >>>> as `strscpy` implicitly has this behavior. >>>> >>>> Link: 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: linux-hardening@xxxxxxxxxxxxxxx >>>> Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx> >>> >>>> arch/x86/platform/uv/uv_nmi.c | 7 +++---- >>>> 1 file changed, 3 insertions(+), 4 deletions(-) >>> >>> Note that this commit is already upstream: >>> >>> 1e6f01f72855 ("x86/platform/uv: Refactor code using deprecated strcpy()/strncpy() interfaces to use strscpy()") >>> >>> Below is the delta your v3 patch has compared to what is upstream - is it >>> really necessary to open code it, instead of using strnchrnul() as your >>> original patch did? Am I missing anything here? >> >> The new version is a result of a review from my because IMHO: >> >> strscpy(arg, val, strnchrnul(val, sizeof(arg)-1, '\n') - val + 1); >> >> Is really unreadable / really hard to reason about if >> this is actually correct and does not contain any >> of by 1 bugs. >> >> Note that the diff of v3 compared to the code before v2 landed is >> actually smaller now and actually matches the subject of: >> "refactor deprecated strcpy and strncpy" >> >> Where as v2 actually touches more code / refactor things >> which fall outside of a "one change per patch" approach. >> The: >> >> p = strchr(arg, '\n'); >> if (p) >> *p = '\0'; >> >> was already there before v2 landed. >> >> I also suggested to do a follow up patch to change things to: >> >> strscpy(arg, val, sizeof(arg)); >> p = strchrnul(arg, '\n'); >> *p = '\0'; >> >> Which IMHO is much more readable then what has landed >> now. But since v2 has already landed I guess the best >> thing is just to stick with what we have upstream now... > > Well, how about we do a delta patch with all the changes > you suggested? I'm all for readability. So I started doing this and notices that all the string manipulation + parsing done here is really just a DYI implementation of sysfs_match_string(). So I have prepared a patch to switch to sysfs_match_string(), which completely removes the need to make a copy of the val string. I'll submit the patch right after this email. Regards, Hans
