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authorChristoph Hellwig <hch@lst.de>2020-06-08 21:34:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-09 09:39:15 -0700
commiteab0c6089b68974ebc6a9a7eab68456eeb6a99c7 (patch)
tree6b03656fac37fc4c4e43c74e33a5fd5b9f3d2b68 /mm
parentcd0309058f849257f08d1a3dd0c384d1fd20c1e8 (diff)
downloadlwn-eab0c6089b68974ebc6a9a7eab68456eeb6a99c7.tar.gz
lwn-eab0c6089b68974ebc6a9a7eab68456eeb6a99c7.zip
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>
Diffstat (limited to 'mm')
-rw-r--r--mm/maccess.c50
1 files changed, 37 insertions, 13 deletions
diff --git a/mm/maccess.c b/mm/maccess.c
index 2526d30739ad..f784da7ed2ad 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -6,6 +6,17 @@
#include <linux/mm.h>
#include <linux/uaccess.h>
+static long __probe_kernel_read(void *dst, const void *src, size_t size,
+ bool strict);
+static long __strncpy_from_unsafe(char *dst, const void *unsafe_addr,
+ long count, bool strict);
+
+bool __weak probe_kernel_read_allowed(const void *unsafe_src, size_t size,
+ bool strict)
+{
+ return true;
+}
+
/**
* probe_kernel_read(): safely attempt to read from any location
* @dst: pointer to the buffer that shall take the data
@@ -19,8 +30,11 @@
* DO NOT USE THIS FUNCTION - it is broken on architectures with entirely
* separate kernel and user address spaces, and also a bad idea otherwise.
*/
-long __weak probe_kernel_read(void *dst, const void *src, size_t size)
- __attribute__((alias("__probe_kernel_read")));
+long probe_kernel_read(void *dst, const void *src, size_t size)
+{
+ return __probe_kernel_read(dst, src, size, false);
+}
+EXPORT_SYMBOL_GPL(probe_kernel_read);
/**
* probe_kernel_read_strict(): safely attempt to read from kernel-space
@@ -36,15 +50,20 @@ long __weak probe_kernel_read(void *dst, const void *src, size_t size)
* probe_kernel_read() suitable for use within regions where the caller
* already holds mmap_lock, or other locks which nest inside mmap_lock.
*/
+long probe_kernel_read_strict(void *dst, const void *src, size_t size)
+{
+ return __probe_kernel_read(dst, src, size, true);
+}
-long __weak probe_kernel_read_strict(void *dst, const void *src, size_t size)
- __attribute__((alias("__probe_kernel_read")));
-
-long __probe_kernel_read(void *dst, const void *src, size_t size)
+static long __probe_kernel_read(void *dst, const void *src, size_t size,
+ bool strict)
{
long ret;
mm_segment_t old_fs = get_fs();
+ if (!probe_kernel_read_allowed(src, size, strict))
+ return -EFAULT;
+
set_fs(KERNEL_DS);
pagefault_disable();
ret = __copy_from_user_inatomic(dst, (__force const void __user *)src,
@@ -56,7 +75,6 @@ long __probe_kernel_read(void *dst, const void *src, size_t size)
return -EFAULT;
return 0;
}
-EXPORT_SYMBOL_GPL(probe_kernel_read);
/**
* probe_user_read(): safely attempt to read from a user-space location
@@ -163,8 +181,10 @@ EXPORT_SYMBOL_GPL(probe_user_write);
* DO NOT USE THIS FUNCTION - it is broken on architectures with entirely
* separate kernel and user address spaces, and also a bad idea otherwise.
*/
-long __weak strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
- __attribute__((alias("__strncpy_from_unsafe")));
+long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
+{
+ return __strncpy_from_unsafe(dst, unsafe_addr, count, false);
+}
/**
* strncpy_from_kernel_nofault: - Copy a NUL terminated string from unsafe
@@ -184,11 +204,13 @@ long __weak strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
* If @count is smaller than the length of the string, copies @count-1 bytes,
* sets the last byte of @dst buffer to NUL and returns @count.
*/
-long __weak strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr,
- long count)
- __attribute__((alias("__strncpy_from_unsafe")));
+long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
+{
+ return __strncpy_from_unsafe(dst, unsafe_addr, count, true);
+}
-long __strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
+static long __strncpy_from_unsafe(char *dst, const void *unsafe_addr,
+ long count, bool strict)
{
mm_segment_t old_fs = get_fs();
const void *src = unsafe_addr;
@@ -196,6 +218,8 @@ long __strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
if (unlikely(count <= 0))
return 0;
+ if (!probe_kernel_read_allowed(unsafe_addr, count, strict))
+ return -EFAULT;
set_fs(KERNEL_DS);
pagefault_disable();