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x86: Unify copy_from_user() size checking
Commits4a31276930
("x86: Turn the copy_from_user check into an (optional) compile time warning") and63312b6a6f
("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 commit9f0cf4adb6
("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 commit2fb0815c9e
("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>
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parent
88829dfe4b
commit
3df7b41aa5
4 changed files with 69 additions and 46 deletions
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@ -542,5 +542,73 @@ extern struct movsl_mask {
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# include <asm/uaccess_64.h>
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#endif
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unsigned long __must_check _copy_from_user(void *to, const void __user *from,
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unsigned n);
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#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
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# define copy_user_diag __compiletime_error
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#else
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# define copy_user_diag __compiletime_warning
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#endif
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extern void copy_user_diag("copy_from_user() buffer size is too small")
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copy_from_user_overflow(void);
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#undef copy_user_diag
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#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
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extern void
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__compiletime_warning("copy_from_user() buffer size is not provably correct")
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__copy_from_user_overflow(void) __asm__("copy_from_user_overflow");
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#define __copy_from_user_overflow(size, count) __copy_from_user_overflow()
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#else
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static inline void
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__copy_from_user_overflow(int size, unsigned long count)
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{
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WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
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}
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#endif
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static inline unsigned long __must_check
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copy_from_user(void *to, const void __user *from, unsigned long n)
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{
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int sz = __compiletime_object_size(to);
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might_fault();
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/*
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* While we would like to have the compiler do the checking for us
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* even in the non-constant size case, any false positives there are
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* a problem (especially when DEBUG_STRICT_USER_COPY_CHECKS, but even
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* without - the [hopefully] dangerous looking nature of the warning
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* would make people go look at the respecitive call sites over and
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* over again just to find that there's no problem).
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*
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* And there are cases where it's just not realistic for the compiler
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* to prove the count to be in range. For example when multiple call
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* sites of a helper function - perhaps in different source files -
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* all doing proper range checking, yet the helper function not doing
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* so again.
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*
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* Therefore limit the compile time checking to the constant size
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* case, and do only runtime checking for non-constant sizes.
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*/
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if (likely(sz < 0 || sz >= n))
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n = _copy_from_user(to, from, n);
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else if(__builtin_constant_p(n))
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copy_from_user_overflow();
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else
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__copy_from_user_overflow(sz, n);
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return n;
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}
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#undef __copy_from_user_overflow
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#endif /* _ASM_X86_UACCESS_H */
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@ -186,31 +186,5 @@ __copy_from_user_inatomic_nocache(void *to, const void __user *from,
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unsigned long __must_check copy_to_user(void __user *to,
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const void *from, unsigned long n);
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unsigned long __must_check _copy_from_user(void *to,
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const void __user *from,
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unsigned long n);
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extern void copy_from_user_overflow(void)
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#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
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__compiletime_error("copy_from_user() buffer size is not provably correct")
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#else
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__compiletime_warning("copy_from_user() buffer size is not provably correct")
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#endif
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;
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static inline unsigned long __must_check copy_from_user(void *to,
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const void __user *from,
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unsigned long n)
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{
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int sz = __compiletime_object_size(to);
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if (likely(sz == -1 || sz >= n))
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n = _copy_from_user(to, from, n);
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else
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copy_from_user_overflow();
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return n;
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}
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#endif /* _ASM_X86_UACCESS_32_H */
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@ -48,26 +48,8 @@ copy_user_generic(void *to, const void *from, unsigned len)
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__must_check unsigned long
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_copy_to_user(void __user *to, const void *from, unsigned len);
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__must_check unsigned long
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_copy_from_user(void *to, const void __user *from, unsigned len);
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__must_check unsigned long
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copy_in_user(void __user *to, const void __user *from, unsigned len);
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static inline unsigned long __must_check copy_from_user(void *to,
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const void __user *from,
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unsigned long n)
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{
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int sz = __compiletime_object_size(to);
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might_fault();
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if (likely(sz == -1 || sz >= n))
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n = _copy_from_user(to, from, n);
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#ifdef CONFIG_DEBUG_VM
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else
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WARN(1, "Buffer overflow detected!\n");
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#endif
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return n;
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}
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static __always_inline __must_check
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int copy_to_user(void __user *dst, const void *src, unsigned size)
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{
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@ -679,8 +679,7 @@ EXPORT_SYMBOL(copy_to_user);
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* If some data could not be copied, this function will pad the copied
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* data to the requested size using zero bytes.
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*/
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unsigned long
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_copy_from_user(void *to, const void __user *from, unsigned long n)
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unsigned long _copy_from_user(void *to, const void __user *from, unsigned n)
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{
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if (access_ok(VERIFY_READ, from, n))
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n = __copy_from_user(to, from, n);
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