On Sun, 2021-08-01 at 09:39 -0700, Joe Perches wrote: > On Sun, 2021-08-01 at 16:00 +0100, Russell King (Oracle) wrote: > > On Sun, Aug 01, 2021 at 04:43:16PM +0200, Len Baker wrote: > > > strcpy() performs no bounds checking on the destination buffer. This > > > could result in linear overflows beyond the end of the buffer, leading > > > to all kinds of misbehaviors. The safe replacement is strscpy(). [] > > So if the string doesn't fit, it's fine to silently truncate it? > > > > Rather than converting every single strcpy() in the kernel to > > strscpy(), maybe there should be some consideration given to how the > > issue of a strcpy() that overflows the buffer should be handled. > > E.g. in the case of a known string such as the above, if it's longer > > than the destination, should we find a way to make the compiler issue > > a warning at compile time? (apologies for the earlier blank reply, sometimes I dislike my email client) stracpy could do that with a trivial addition like below: Old lkml references: https://lore.kernel.org/lkml/cover.1563889130.git.joe@xxxxxxxxxxx/ and https://lore.kernel.org/lkml/56dc4de7e0db153cb10954ac251cb6c27c33da4a.camel@xxxxxxxxxxx/ But Linus T wants a copy_string mechanism instead: https://lore.kernel.org/lkml/CAHk-=wgqQKoAnhmhGE-2PBFt7oQs9LLAATKbYa573UO=DPBE0Q@xxxxxxxxxxxxxx/ /** * stracpy - Copy a C-string into an array of char/u8/s8 or equivalent * @dest: Where to copy the string, must be an array of char and not a pointer * @src: String to copy, may be a pointer or const char array * * Helper for strscpy(). * Copies a maximum of sizeof(@dest) bytes of @src with %NUL termination. * * A BUILD_BUG_ON is used for cases where @dest is not a char array or * @src is a char array and is larger than @dest. * * Returns: * * The number of characters copied (not including the trailing %NUL) * * -E2BIG if @dest is a zero size array or @src was truncated. */ #define stracpy(dest, src) \ ({ \ BUILD_BUG_ON(!(__same_type(dest, char[]) || \ __same_type(dest, unsigned char[]) || \ __same_type(dest, signed char[]))); \ BUILD_BUG_ON((__same_type(src, char[]) || \ __same_type(src, unsigned char[]) || \ __same_type(src, signed char[])) && \ ARRAY_SIZE(src) > ARRAY_SIZE(dest)); \ \ strscpy(dest, src, ARRAY_SIZE(dest)); \ })
