maccess: unify the probe kernel arch hooks

Currently architectures have to override every routine that probes
kernel memory, which includes a pure read and strcpy, both in strict
and not strict variants.  Just provide a single arch hooks instead to
make sure all architectures cover all the cases.

[akpm@linux-foundation.org: fix !CONFIG_X86_64 build]

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20200521152301.2587579-11-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 21 deletions

diff --git a/arch/x86/mm/maccess.c b/arch/x86/mm/maccess.c
index 62c4017a2473..86000c1150e8 100644
--- a/arch/x86/mm/maccess.c
+++ b/arch/x86/mm/maccess.c
@@ -9,35 +9,26 @@ static __always_inline u64 canonical_address(u64 vaddr, u8 vaddr_bits)
 	return ((s64)vaddr << (64 - vaddr_bits)) >> (64 - vaddr_bits);
 }
 
-static __always_inline bool invalid_probe_range(u64 vaddr)
+bool probe_kernel_read_allowed(const void *unsafe_src, size_t size, bool strict)
 {
+	unsigned long vaddr = (unsigned long)unsafe_src;
+
+	if (!strict)
+		return true;
+
 	/*
 	 * Range covering the highest possible canonical userspace address
 	 * as well as non-canonical address range. For the canonical range
 	 * we also need to include the userspace guard page.
 	 */
-	return vaddr < TASK_SIZE_MAX + PAGE_SIZE ||
-	       canonical_address(vaddr, boot_cpu_data.x86_virt_bits) != vaddr;
+	return vaddr >= TASK_SIZE_MAX + PAGE_SIZE &&
+	       canonical_address(vaddr, boot_cpu_data.x86_virt_bits) == vaddr;
 }
 #else
-static __always_inline bool invalid_probe_range(u64 vaddr)
+bool probe_kernel_read_allowed(const void *unsafe_src, size_t size, bool strict)
 {
-	return vaddr < TASK_SIZE_MAX;
+	if (!strict)
+		return true;
+	return (unsigned long)unsafe_src >= TASK_SIZE_MAX;
 }
 #endif
-
-long probe_kernel_read_strict(void *dst, const void *src, size_t size)
-{
-	if (unlikely(invalid_probe_range((unsigned long)src)))
-		return -EFAULT;
-
-	return __probe_kernel_read(dst, src, size);
-}
-
-long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
-{
-	if (unlikely(invalid_probe_range((unsigned long)unsafe_addr)))
-		return -EFAULT;
-
-	return __strncpy_from_unsafe(dst, unsafe_addr, count);
-}