Date: Wed, 20 Feb 2019 17:05:10 -0800 From: Kees Cook <keescook@...omium.org> To: Jann Horn <jannh@...gle.com> Cc: "Tobin C. Harding" <tobin@...nel.org>, Shuah Khan <shuah@...nel.org>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, kernel list <linux-kernel@...r.kernel.org>, Andy Lutomirski <luto@...capital.net>, Rasmus Villemoes <linux@...musvillemoes.dk>, Daniel Micay <danielmicay@...il.com> Subject: Re: [PATCH 5/6] lib: Fix function documentation for strncpy_from_user On Mon, Feb 18, 2019 at 4:52 PM Jann Horn <jannh@...gle.com> wrote: > AFAICS the byte_at_a_time loop exits when max==0 is reached, and then > if `res >= count` (in other words, if we've copied as many bytes as > requested, haven't encountered a null byte so far, and haven't reached > the end of the address space), we return `res`, which is the same as > `count`. Are you sure? Oh, whew, there is only 1 arch-specific implementation of this. I thought you meant there was multiple implementations. So, generally speaking, I'd love to split all strncpy* uses into strscpy_zero() (when expecting to do str->str copies), and some new function, named like mempadstr() or str2mem() that copies a str to a __nonstring char array, with trailing padding, if there is space. Then there is no more mixing the two cases and botching things. -- Kees Cook
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