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charset=us-ascii Content-Disposition: inline In-Reply-To: <20240208-alice-mm-v2-2-d821250204a6@google.com> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 60A7014001C X-Stat-Signature: fu9b6zodceii1147e5a7dbpbneh9iunp X-HE-Tag: 1707524117-578342 X-HE-Meta: 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 NAY4HI8b WvqYR605+JOLEnXdS2Wep9gKkDHxFlwDc0Cgf6TcFg5xFET+9FqsMgUBH/rRqZ3AXMRjjBstbUzgzCx0YGQ7wW4zzj0Epf0leYCOJGaviz67wH6P4I4fCMmk8NpMGAhZvrprp9etaD/IsBr2Eu1TPXj4E6lQUjinRFykdREL3owUZ/0V4bsFPrfSZs8v8Nfx4KbEBv2/IwVVACF4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Feb 08, 2024 at 03:47:52PM +0000, Alice Ryhl wrote: > From: Arnd Bergmann > > Rust code needs to be able to access _copy_from_user and _copy_to_user > so that it can skip the check_copy_size check in cases where the length > is known at compile-time, mirroring the logic for when C code will skip > check_copy_size. To do this, we ensure that exported versions of these > methods are available when CONFIG_RUST is enabled. > > Signed-off-by: Arnd Bergmann > Signed-off-by: Alice Ryhl > --- > include/linux/uaccess.h | 37 +++++++++++++++++++++++-------------- > lib/usercopy.c | 30 ++++-------------------------- > 2 files changed, 27 insertions(+), 40 deletions(-) > > diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h > index 3064314f4832..835aa175d0ee 100644 > --- a/include/linux/uaccess.h > +++ b/include/linux/uaccess.h > @@ -138,13 +138,18 @@ __copy_to_user(void __user *to, const void *from, unsigned long n) > return raw_copy_to_user(to, from, n); > } > > -#ifdef INLINE_COPY_FROM_USER > static inline __must_check unsigned long > -_copy_from_user(void *to, const void __user *from, unsigned long n) > +_inline_copy_from_user(void *to, const void __user *from, unsigned long n) > { > unsigned long res = n; > might_fault(); > if (!should_fail_usercopy() && likely(access_ok(from, n))) { > + /* > + * Ensure that bad access_ok() speculation will not > + * lead to nasty side effects *after* the copy is > + * finished: > + */ > + barrier_nospec(); This means all callers just gained this barrier. That's a behavioral change -- is it intentional here? I don't see it mentioned in the commit log. Also did this get tested with the CONFIG_TEST_USER_COPY tests? I would expect it to be fine, but better to check and mention it in the commit log. -Kees > instrument_copy_from_user_before(to, from, n); > res = raw_copy_from_user(to, from, n); > instrument_copy_from_user_after(to, from, n, res); > @@ -153,14 +158,11 @@ _copy_from_user(void *to, const void __user *from, unsigned long n) > memset(to + (n - res), 0, res); > return res; > } > -#else > extern __must_check unsigned long > _copy_from_user(void *, const void __user *, unsigned long); > -#endif > > -#ifdef INLINE_COPY_TO_USER > static inline __must_check unsigned long > -_copy_to_user(void __user *to, const void *from, unsigned long n) > +_inline_copy_to_user(void __user *to, const void *from, unsigned long n) > { > might_fault(); > if (should_fail_usercopy()) > @@ -171,25 +173,32 @@ _copy_to_user(void __user *to, const void *from, unsigned long n) > } > return n; > } > -#else > extern __must_check unsigned long > _copy_to_user(void __user *, const void *, unsigned long); > -#endif > > static __always_inline unsigned long __must_check > copy_from_user(void *to, const void __user *from, unsigned long n) > { > - if (check_copy_size(to, n, false)) > - n = _copy_from_user(to, from, n); > - return n; > + if (!check_copy_size(to, n, false)) > + return n; > +#ifdef INLINE_COPY_FROM_USER > + return _inline_copy_from_user(to, from, n); > +#else > + return _copy_from_user(to, from, n); > +#endif > } > > static __always_inline unsigned long __must_check > copy_to_user(void __user *to, const void *from, unsigned long n) > { > - if (check_copy_size(from, n, true)) > - n = _copy_to_user(to, from, n); > - return n; > + if (!check_copy_size(from, n, true)) > + return n; > + > +#ifdef INLINE_COPY_TO_USER > + return _inline_copy_to_user(to, from, n); > +#else > + return _copy_to_user(to, from, n); > +#endif > } > > #ifndef copy_mc_to_kernel > diff --git a/lib/usercopy.c b/lib/usercopy.c > index d29fe29c6849..de7f30618293 100644 > --- a/lib/usercopy.c > +++ b/lib/usercopy.c > @@ -7,40 +7,18 @@ > > /* out-of-line parts */ > > -#ifndef INLINE_COPY_FROM_USER > +#if !defined(INLINE_COPY_FROM_USER) || defined(CONFIG_RUST) > unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n) > { > - unsigned long res = n; > - might_fault(); > - if (!should_fail_usercopy() && likely(access_ok(from, n))) { > - /* > - * Ensure that bad access_ok() speculation will not > - * lead to nasty side effects *after* the copy is > - * finished: > - */ > - barrier_nospec(); > - instrument_copy_from_user_before(to, from, n); > - res = raw_copy_from_user(to, from, n); > - instrument_copy_from_user_after(to, from, n, res); > - } > - if (unlikely(res)) > - memset(to + (n - res), 0, res); > - return res; > + return _inline_copy_from_user(to, from, n); > } > EXPORT_SYMBOL(_copy_from_user); > #endif > > -#ifndef INLINE_COPY_TO_USER > +#if !defined(INLINE_COPY_TO_USER) || defined(CONFIG_RUST) > unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n) > { > - might_fault(); > - if (should_fail_usercopy()) > - return n; > - if (likely(access_ok(to, n))) { > - instrument_copy_to_user(to, from, n); > - n = raw_copy_to_user(to, from, n); > - } > - return n; > + return _inline_copy_to_user(to, from, n); > } > EXPORT_SYMBOL(_copy_to_user); > #endif > > -- > 2.43.0.594.gd9cf4e227d-goog > -- Kees Cook