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maccess: return -ERANGE when probe_kernel_read() fails 

Allow the callers to distinguish a real unmapped address vs a range
that can't be probed.

Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.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: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20200521152301.2587579-24-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Christoph Hellwig 2020-06-08 21:35:04 -07:00 committed by Linus Torvalds
parent fa94111d94
commit 2a71e81d32
1 changed files with 9 additions and 7 deletions
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16
mm/maccess.c
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@ -24,7 +24,7 @@ bool __weak probe_kernel_read_allowed(const void *unsafe_src, size_t size)
long probe_kernel_read(void *dst, const void *src, size_t size)
{
if (!probe_kernel_read_allowed(src, size))
return -EFAULT;
return -ERANGE;
pagefault_disable();
probe_kernel_read_loop(dst, src, size, u64, Efault);
@ -68,7 +68,7 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
if (unlikely(count <= 0))
return 0;
if (!probe_kernel_read_allowed(unsafe_addr, count))
return -EFAULT;
return -ERANGE;
pagefault_disable();
do {
@ -93,7 +93,8 @@ Efault:
* @size: size of the data chunk
*
* Safely read from kernel address @src to the buffer at @dst. If a kernel
* fault happens, handle that and return -EFAULT.
* fault happens, handle that and return -EFAULT. If @src is not a valid kernel
* address, return -ERANGE.
*
* We ensure that the copy_from_user is executed in atomic context so that
* do_page_fault() doesn't attempt to take mmap_lock. This makes
@ -106,7 +107,7 @@ long probe_kernel_read(void *dst, const void *src, size_t size)
mm_segment_t old_fs = get_fs();
if (!probe_kernel_read_allowed(src, size))
return -EFAULT;
return -ERANGE;
set_fs(KERNEL_DS);
pagefault_disable();
@ -158,8 +159,9 @@ long probe_kernel_write(void *dst, const void *src, size_t size)
*
* On success, returns the length of the string INCLUDING the trailing NUL.
*
* If access fails, returns -EFAULT (some data may have been copied
* and the trailing NUL added).
* If access fails, returns -EFAULT (some data may have been copied and the
* trailing NUL added). If @unsafe_addr is not a valid kernel address, return
* -ERANGE.
*
* 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.
@ -173,7 +175,7 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
if (unlikely(count <= 0))
return 0;
if (!probe_kernel_read_allowed(unsafe_addr, count))
return -EFAULT;
return -ERANGE;
set_fs(KERNEL_DS);
pagefault_disable();