From 3df7b41aa5e7797f391d0a41f8b0dce1fe366a09 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 21 Oct 2013 09:43:57 +0100 Subject: 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 Cc: Arjan van de Ven Cc: Guenter Roeck Cc: Linus Torvalds Cc: Andrew Morton Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/5265056D02000078000FC4F3@nat28.tlf.novell.com Signed-off-by: Ingo Molnar --- arch/x86/lib/usercopy_32.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'arch/x86/lib') 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); * 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); -- cgit v1.2.1 From 7a3d9b0f3abbea957b829cdfff8169872c575642 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 21 Oct 2013 09:44:37 +0100 Subject: x86: Unify copy_to_user() and add size checking to it Similarly to copy_from_user(), where the range check is to protect against kernel memory corruption, copy_to_user() can benefit from such checking too: Here it protects against kernel information leaks. Signed-off-by: Jan Beulich Cc: Cc: Linus Torvalds Cc: Andrew Morton Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/5265059502000078000FC4F6@nat28.tlf.novell.com Signed-off-by: Ingo Molnar Cc: Arjan van de Ven --- arch/x86/lib/usercopy_32.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'arch/x86/lib') diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c index c408d0222917..e2f5e21c03b3 100644 --- a/arch/x86/lib/usercopy_32.c +++ b/arch/x86/lib/usercopy_32.c @@ -654,14 +654,13 @@ EXPORT_SYMBOL(__copy_from_user_ll_nocache_nozero); * Returns number of bytes that could not be copied. * On success, this will be zero. */ -unsigned long -copy_to_user(void __user *to, const void *from, unsigned long n) +unsigned long _copy_to_user(void __user *to, const void *from, unsigned n) { if (access_ok(VERIFY_WRITE, to, n)) n = __copy_to_user(to, from, n); return n; } -EXPORT_SYMBOL(copy_to_user); +EXPORT_SYMBOL(_copy_to_user); /** * copy_from_user: - Copy a block of data from user space. -- cgit v1.2.1