Date: Tue, 19 Feb 2019 03:12:33 +0100 From: Jann Horn <jannh@...gle.com> To: "Tobin C. Harding" <tobin@...nel.org> Cc: Kees Cook <keescook@...omium.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> Subject: Re: [PATCH 6/6] lib: Add function strscpy_from_user() On Tue, Feb 19, 2019 at 12:25 AM Tobin C. Harding <tobin@...nel.org> wrote: > Currently we have strncpy_from_userspace(). If the user string is > longer than the destination kernel buffer we get an error code -EFAULT. > We are unable to recover from here because this is the same error > returned if the access to userspace fails totally. > > There is no reason we cannot continue execution with the user string > truncated. > > Add a function strscpy_from_user() that guarantees the string written is > null-terminated. If user string is longer than destination buffer > truncates the string. Returns the number of characters written > excluding the null-terminator. > > Signed-off-by: Tobin C. Harding <tobin@...nel.org> > --- > lib/strncpy_from_user.c | 43 +++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 43 insertions(+) > > diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c > index 11fe9a4a00fd..6bd603ccec7a 100644 > --- a/lib/strncpy_from_user.c > +++ b/lib/strncpy_from_user.c This file is only built when CONFIG_GENERIC_STRNCPY_FROM_USER is set. Some architectures have their own versions of strncpy_from_user() and don't set that, so on those architectures, your code wouldn't be built into the kernel.
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