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authorJan Beulich <JBeulich@suse.com>2013-10-21 04:43:57 -0400
committerIngo Molnar <mingo@kernel.org>2013-10-26 06:27:36 -0400
commit3df7b41aa5e7797f391d0a41f8b0dce1fe366a09 (patch)
treef79334f0230b5728f1b541e1ef500373c0f764a6
parent88829dfe4b6ea0c1c24d415668b3bfa78e5a5b16 (diff)
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.h68
-rw-r--r--arch/x86/include/asm/uaccess_32.h26
-rw-r--r--arch/x86/include/asm/uaccess_64.h18
-rw-r--r--arch/x86/lib/usercopy_32.c3
4 files changed, 69 insertions, 46 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 5838fa911aa0..c9799ed208a8 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -542,5 +542,73 @@ extern struct movsl_mask {
542# include <asm/uaccess_64.h> 542# include <asm/uaccess_64.h>
543#endif 543#endif
544 544
545unsigned long __must_check _copy_from_user(void *to, const void __user *from,
546 unsigned n);
547
548#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
549# define copy_user_diag __compiletime_error
550#else
551# define copy_user_diag __compiletime_warning
552#endif
553
554extern void copy_user_diag("copy_from_user() buffer size is too small")
555copy_from_user_overflow(void);
556
557#undef copy_user_diag
558
559#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
560
561extern void
562__compiletime_warning("copy_from_user() buffer size is not provably correct")
563__copy_from_user_overflow(void) __asm__("copy_from_user_overflow");
564#define __copy_from_user_overflow(size, count) __copy_from_user_overflow()
565
566#else
567
568static inline void
569__copy_from_user_overflow(int size, unsigned long count)
570{
571 WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
572}
573
574#endif
575
576static inline unsigned long __must_check
577copy_from_user(void *to, const void __user *from, unsigned long n)
578{
579 int sz = __compiletime_object_size(to);
580
581 might_fault();
582
583 /*
584 * While we would like to have the compiler do the checking for us
585 * even in the non-constant size case, any false positives there are
586 * a problem (especially when DEBUG_STRICT_USER_COPY_CHECKS, but even
587 * without - the [hopefully] dangerous looking nature of the warning
588 * would make people go look at the respecitive call sites over and
589 * over again just to find that there's no problem).
590 *
591 * And there are cases where it's just not realistic for the compiler
592 * to prove the count to be in range. For example when multiple call
593 * sites of a helper function - perhaps in different source files -
594 * all doing proper range checking, yet the helper function not doing
595 * so again.
596 *
597 * Therefore limit the compile time checking to the constant size
598 * case, and do only runtime checking for non-constant sizes.
599 */
600
601 if (likely(sz < 0 || sz >= n))
602 n = _copy_from_user(to, from, n);
603 else if(__builtin_constant_p(n))
604 copy_from_user_overflow();
605 else
606 __copy_from_user_overflow(sz, n);
607
608 return n;
609}
610
611#undef __copy_from_user_overflow
612
545#endif /* _ASM_X86_UACCESS_H */ 613#endif /* _ASM_X86_UACCESS_H */
546 614
diff --git a/arch/x86/include/asm/uaccess_32.h b/arch/x86/include/asm/uaccess_32.h
index 7f760a9f1f61..c348c87cefc8 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,
186 186
187unsigned long __must_check copy_to_user(void __user *to, 187unsigned long __must_check copy_to_user(void __user *to,
188 const void *from, unsigned long n); 188 const void *from, unsigned long n);
189unsigned long __must_check _copy_from_user(void *to,
190 const void __user *from,
191 unsigned long n);
192
193
194extern void copy_from_user_overflow(void)
195#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
196 __compiletime_error("copy_from_user() buffer size is not provably correct")
197#else
198 __compiletime_warning("copy_from_user() buffer size is not provably correct")
199#endif
200;
201
202static inline unsigned long __must_check copy_from_user(void *to,
203 const void __user *from,
204 unsigned long n)
205{
206 int sz = __compiletime_object_size(to);
207
208 if (likely(sz == -1 || sz >= n))
209 n = _copy_from_user(to, from, n);
210 else
211 copy_from_user_overflow();
212
213 return n;
214}
215 189
216#endif /* _ASM_X86_UACCESS_32_H */ 190#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 4f7923dd0007..4df93c46852b 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)
48__must_check unsigned long 48__must_check unsigned long
49_copy_to_user(void __user *to, const void *from, unsigned len); 49_copy_to_user(void __user *to, const void *from, unsigned len);
50__must_check unsigned long 50__must_check unsigned long
51_copy_from_user(void *to, const void __user *from, unsigned len);
52__must_check unsigned long
53copy_in_user(void __user *to, const void __user *from, unsigned len); 51copy_in_user(void __user *to, const void __user *from, unsigned len);
54 52
55static inline unsigned long __must_check copy_from_user(void *to,
56 const void __user *from,
57 unsigned long n)
58{
59 int sz = __compiletime_object_size(to);
60
61 might_fault();
62 if (likely(sz == -1 || sz >= n))
63 n = _copy_from_user(to, from, n);
64#ifdef CONFIG_DEBUG_VM
65 else
66 WARN(1, "Buffer overflow detected!\n");
67#endif
68 return n;
69}
70
71static __always_inline __must_check 53static __always_inline __must_check
72int copy_to_user(void __user *dst, const void *src, unsigned size) 54int copy_to_user(void __user *dst, const void *src, unsigned size)
73{ 55{
diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c
index 3eb18acd0e40..c408d0222917 100644
--- a/arch/x86/lib/usercopy_32.c
+++ b/arch/x86/lib/usercopy_32.c
@@ -679,8 +679,7 @@ EXPORT_SYMBOL(copy_to_user);
679 * If some data could not be copied, this function will pad the copied 679 * If some data could not be copied, this function will pad the copied
680 * data to the requested size using zero bytes. 680 * data to the requested size using zero bytes.
681 */ 681 */
682unsigned long 682unsigned long _copy_from_user(void *to, const void __user *from, unsigned n)
683_copy_from_user(void *to, const void __user *from, unsigned long n)
684{ 683{
685 if (access_ok(VERIFY_READ, from, n)) 684 if (access_ok(VERIFY_READ, from, n))
686 n = __copy_from_user(to, from, n); 685 n = __copy_from_user(to, from, n);