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author | Jan Beulich <JBeulich@suse.com> | 2013-10-21 08:43:57 (GMT) |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2013-10-26 10:27:36 (GMT) |
commit | 3df7b41aa5e7797f391d0a41f8b0dce1fe366a09 (patch) | |
tree | f79334f0230b5728f1b541e1ef500373c0f764a6 | |
parent | 88829dfe4b6ea0c1c24d415668b3bfa78e5a5b16 (diff) | |
download | linux-fsl-qoriq-3df7b41aa5e7797f391d0a41f8b0dce1fe366a09.tar.xz |
x86: Unify copy_from_user() size checking
Commits 4a3127693001c61a21d1ce680db6340623f52e93 ("x86: Turn the
copy_from_user check into an (optional) compile time warning")
and 63312b6a6faae3f2e5577f2b001e3b504f10a2aa ("x86: Add a
Kconfig option to turn the copy_from_user warnings into errors")
touched only the 32-bit variant of copy_from_user(), whereas the
original commit 9f0cf4adb6aa0bfccf675c938124e68f7f06349d ("x86:
Use __builtin_object_size() to validate the buffer size for
copy_from_user()") also added the same code to the 64-bit one.
Further the earlier conversion from an inline WARN() to the call
to copy_from_user_overflow() went a little too far: When the
number of bytes to be copied is not a constant (e.g. [looking at
3.11] in drivers/net/tun.c:__tun_chr_ioctl() or
drivers/pci/pcie/aer/aer_inject.c:aer_inject_write()), the
compiler will always have to keep the funtion call, and hence
there will always be a warning. By using __builtin_constant_p()
we can avoid this.
And then this slightly extends the effect of
CONFIG_DEBUG_STRICT_USER_COPY_CHECKS in that apart from
converting warnings to errors in the constant size case, it
retains the (possibly wrong) warnings in the non-constant size
case, such that if someone is prepared to get a few false
positives, (s)he'll be able to recover the current behavior
(except that these diagnostics now will never be converted to
errors).
Since the 32-bit variant (intentionally) didn't call
might_fault(), the unification results in this being called
twice now. Adding a suitable #ifdef would be the alternative if
that's a problem.
I'd like to point out though that with
__compiletime_object_size() being restricted to gcc before 4.6,
the whole construct is going to become more and more pointless
going forward. I would question however that commit
2fb0815c9ee6b9ac50e15dd8360ec76d9fa46a2 ("gcc4: disable
__compiletime_object_size for GCC 4.6+") was really necessary,
and instead this should have been dealt with as is done here
from the beginning.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/5265056D02000078000FC4F3@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r-- | arch/x86/include/asm/uaccess.h | 68 | ||||
-rw-r--r-- | arch/x86/include/asm/uaccess_32.h | 26 | ||||
-rw-r--r-- | arch/x86/include/asm/uaccess_64.h | 18 | ||||
-rw-r--r-- | arch/x86/lib/usercopy_32.c | 3 |
4 files changed, 69 insertions, 46 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 5838fa9..c9799ed 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -542,5 +542,73 @@ extern struct movsl_mask { # include <asm/uaccess_64.h> #endif +unsigned long __must_check _copy_from_user(void *to, const void __user *from, + unsigned n); + +#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS +# define copy_user_diag __compiletime_error +#else +# define copy_user_diag __compiletime_warning +#endif + +extern void copy_user_diag("copy_from_user() buffer size is too small") +copy_from_user_overflow(void); + +#undef copy_user_diag + +#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS + +extern void +__compiletime_warning("copy_from_user() buffer size is not provably correct") +__copy_from_user_overflow(void) __asm__("copy_from_user_overflow"); +#define __copy_from_user_overflow(size, count) __copy_from_user_overflow() + +#else + +static inline void +__copy_from_user_overflow(int size, unsigned long count) +{ + WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count); +} + +#endif + +static inline unsigned long __must_check +copy_from_user(void *to, const void __user *from, unsigned long n) +{ + int sz = __compiletime_object_size(to); + + might_fault(); + + /* + * While we would like to have the compiler do the checking for us + * even in the non-constant size case, any false positives there are + * a problem (especially when DEBUG_STRICT_USER_COPY_CHECKS, but even + * without - the [hopefully] dangerous looking nature of the warning + * would make people go look at the respecitive call sites over and + * over again just to find that there's no problem). + * + * And there are cases where it's just not realistic for the compiler + * to prove the count to be in range. For example when multiple call + * sites of a helper function - perhaps in different source files - + * all doing proper range checking, yet the helper function not doing + * so again. + * + * Therefore limit the compile time checking to the constant size + * case, and do only runtime checking for non-constant sizes. + */ + + if (likely(sz < 0 || sz >= n)) + n = _copy_from_user(to, from, n); + else if(__builtin_constant_p(n)) + copy_from_user_overflow(); + else + __copy_from_user_overflow(sz, n); + + return n; +} + +#undef __copy_from_user_overflow + #endif /* _ASM_X86_UACCESS_H */ diff --git a/arch/x86/include/asm/uaccess_32.h b/arch/x86/include/asm/uaccess_32.h index 7f760a9..c348c87 100644 --- a/arch/x86/include/asm/uaccess_32.h +++ b/arch/x86/include/asm/uaccess_32.h @@ -186,31 +186,5 @@ __copy_from_user_inatomic_nocache(void *to, const void __user *from, unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n); -unsigned long __must_check _copy_from_user(void *to, - const void __user *from, - unsigned long n); - - -extern void copy_from_user_overflow(void) -#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS - __compiletime_error("copy_from_user() buffer size is not provably correct") -#else - __compiletime_warning("copy_from_user() buffer size is not provably correct") -#endif -; - -static inline unsigned long __must_check copy_from_user(void *to, - const void __user *from, - unsigned long n) -{ - int sz = __compiletime_object_size(to); - - if (likely(sz == -1 || sz >= n)) - n = _copy_from_user(to, from, n); - else - copy_from_user_overflow(); - - return n; -} #endif /* _ASM_X86_UACCESS_32_H */ diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h index 4f7923d..4df93c4 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -48,26 +48,8 @@ copy_user_generic(void *to, const void *from, unsigned len) __must_check unsigned long _copy_to_user(void __user *to, const void *from, unsigned len); __must_check unsigned long -_copy_from_user(void *to, const void __user *from, unsigned len); -__must_check unsigned long copy_in_user(void __user *to, const void __user *from, unsigned len); -static inline unsigned long __must_check copy_from_user(void *to, - const void __user *from, - unsigned long n) -{ - int sz = __compiletime_object_size(to); - - might_fault(); - if (likely(sz == -1 || sz >= n)) - n = _copy_from_user(to, from, n); -#ifdef CONFIG_DEBUG_VM - else - WARN(1, "Buffer overflow detected!\n"); -#endif - return n; -} - static __always_inline __must_check int copy_to_user(void __user *dst, const void *src, unsigned size) { diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c index 3eb18ac..c408d02 100644 --- a/arch/x86/lib/usercopy_32.c +++ b/arch/x86/lib/usercopy_32.c @@ -679,8 +679,7 @@ EXPORT_SYMBOL(copy_to_user); * If some data could not be copied, this function will pad the copied * data to the requested size using zero bytes. */ -unsigned long -_copy_from_user(void *to, const void __user *from, unsigned long n) +unsigned long _copy_from_user(void *to, const void __user *from, unsigned n) { if (access_ok(VERIFY_READ, from, n)) n = __copy_from_user(to, from, n); |