From: Andrew Donnellan ajd@linux.ibm.com
stable inclusion from linux-4.19.159 commit 92e7ec289b955384fba88953584562ce43164fa7 CVE: CVE-2020-4788
--------------------------------
commit 61e3acd8c693a14fc69b824cb5b08d02cb90a6e7 upstream.
The KUAP implementation adds calls in clear_user() to enable and disable access to userspace memory. However, it doesn't add these to __clear_user(), which is used in the ptrace regset code.
As there's only one direct user of __clear_user() (the regset code), and the time taken to set the AMR for KUAP purposes is going to dominate the cost of a quick access_ok(), there's not much point having a separate path.
Rename __clear_user() to __arch_clear_user(), and make __clear_user() just call clear_user().
Reported-by: syzbot+f25ecf4b2982d8c7a640@syzkaller-ppc64.appspotmail.com Reported-by: Daniel Axtens dja@axtens.net Suggested-by: Michael Ellerman mpe@ellerman.id.au Fixes: de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access Protection") Signed-off-by: Andrew Donnellan ajd@linux.ibm.com [mpe: Use __arch_clear_user() for the asm version like arm64 & nds32] Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20191209132221.15328-1-ajd@linux.ibm.com Signed-off-by: Daniel Axtens dja@axtens.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com Reviewed-by: Jason Yan yanaijie@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- arch/powerpc/include/asm/uaccess.h | 9 +++++++-- arch/powerpc/lib/string_32.S | 4 ++-- arch/powerpc/lib/string_64.S | 6 +++--- 3 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index a7441b7560c7..476fa942500c 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -416,7 +416,7 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n) return ret; }
-extern unsigned long __clear_user(void __user *addr, unsigned long size); +unsigned long __arch_clear_user(void __user *addr, unsigned long size);
static inline unsigned long clear_user(void __user *addr, unsigned long size) { @@ -424,12 +424,17 @@ static inline unsigned long clear_user(void __user *addr, unsigned long size) might_fault(); if (likely(access_ok(VERIFY_WRITE, addr, size))) { allow_write_to_user(addr, size); - ret = __clear_user(addr, size); + ret = __arch_clear_user(addr, size); prevent_write_to_user(addr, size); } return ret; }
+static inline unsigned long __clear_user(void __user *addr, unsigned long size) +{ + return clear_user(addr, size); +} + extern long strncpy_from_user(char *dst, const char __user *src, long count); extern __must_check long strnlen_user(const char __user *str, long n);
diff --git a/arch/powerpc/lib/string_32.S b/arch/powerpc/lib/string_32.S index f69a6aab7bfb..1ddb26394e8a 100644 --- a/arch/powerpc/lib/string_32.S +++ b/arch/powerpc/lib/string_32.S @@ -17,7 +17,7 @@ CACHELINE_BYTES = L1_CACHE_BYTES LG_CACHELINE_BYTES = L1_CACHE_SHIFT CACHELINE_MASK = (L1_CACHE_BYTES-1)
-_GLOBAL(__clear_user) +_GLOBAL(__arch_clear_user) /* * Use dcbz on the complete cache lines in the destination * to set them to zero. This requires that the destination @@ -87,4 +87,4 @@ _GLOBAL(__clear_user) EX_TABLE(8b, 91b) EX_TABLE(9b, 91b)
-EXPORT_SYMBOL(__clear_user) +EXPORT_SYMBOL(__arch_clear_user) diff --git a/arch/powerpc/lib/string_64.S b/arch/powerpc/lib/string_64.S index 56aac4c22025..ea3798f4f25f 100644 --- a/arch/powerpc/lib/string_64.S +++ b/arch/powerpc/lib/string_64.S @@ -29,7 +29,7 @@ PPC64_CACHES: .section ".text"
/** - * __clear_user: - Zero a block of memory in user space, with less checking. + * __arch_clear_user: - Zero a block of memory in user space, with less checking. * @to: Destination address, in user space. * @n: Number of bytes to zero. * @@ -70,7 +70,7 @@ err3; stb r0,0(r3) mr r3,r4 blr
-_GLOBAL_TOC(__clear_user) +_GLOBAL_TOC(__arch_clear_user) cmpdi r4,32 neg r6,r3 li r0,0 @@ -193,4 +193,4 @@ err1; dcbz 0,r3 cmpdi r4,32 blt .Lshort_clear b .Lmedium_clear -EXPORT_SYMBOL(__clear_user) +EXPORT_SYMBOL(__arch_clear_user)