Hi Kees, On Wed, Aug 28, 2024 at 06:48:39AM GMT, Kees Cook wrote: [...] > >Thank you for your suggestion. How does the following commit log look > >to you? Does it meet your expectations? > > > > string: Use ARRAY_SIZE() in strscpy() > > > > We can use ARRAY_SIZE() instead to clarify that they are regular characters. > > > > Co-developed-by: Alejandro Colomar <alx@xxxxxxxxxx> > > Signed-off-by: Alejandro Colomar <alx@xxxxxxxxxx> > > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx> > > > >diff --git a/arch/um/include/shared/user.h b/arch/um/include/shared/user.h > >index bbab79c0c074..07216996e3a9 100644 > >--- a/arch/um/include/shared/user.h > >+++ b/arch/um/include/shared/user.h > >@@ -14,7 +14,7 @@ > > * copying too much infrastructure for my taste, so userspace files > > * get less checking than kernel files. > > */ > >-#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) > >+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]) + __must_be_array(x)) > > > > /* This is to get size_t and NULL */ > > #ifndef __UM_HOST__ > >@@ -60,7 +60,7 @@ static inline void print_hex_dump(const char *level, > >const char *prefix_str, > > extern int in_aton(char *str); > > extern size_t strlcat(char *, const char *, size_t); > > extern size_t sized_strscpy(char *, const char *, size_t); > >-#define strscpy(dst, src) sized_strscpy(dst, src, sizeof(dst)) > >+#define strscpy(dst, src) sized_strscpy(dst, src, ARRAY_SIZE(dst)) > > Uh, but why? strscpy() copies bytes, not array elements. Using sizeof() is already correct and using ARRAY_SIZE() could lead to unexpectedly small counts (in admittedly odd situations). > > What is the problem you're trying to solve here? I suggested that here: <https://lore.kernel.org/all/2jxak5v6dfxlpbxhpm3ey7oup4g2lnr3ueurfbosf5wdo65dk4@srb3hsk72zwq/> There, you'll find the rationale (and also for avoiding the _pad calls where not necessary --I ignore if it's necessary here--). Have a lovely day! Alex > > -Kees > > -- > Kees Cook -- <https://www.alejandro-colomar.es/>
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