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UPSTREAM: maccess: unify the probe kernel arch hooks

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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.

[[email protected]: fix !CONFIG_X86_64 build]

Change-Id: I442209ab9688f814106ececddb672e6250b1a96e
Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Christoph Hellwig 2020-06-08 21:34:27 -07:00 • committed by basamaryan
commit 59deca6737
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GPG key ID: 210D5384FB2A5885
5 changed files with 61 additions and 50 deletions
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50
mm/maccess.c
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@ -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_sem, or other locks which nest inside mmap_sem.
*/
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
@ -164,8 +182,10 @@ 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
@ -185,11 +205,13 @@ 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;
@ -197,6 +219,8 @@ 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();