Commit 7f6aaf1d authored Nov 01, 2018 by Isaac J. Manjarres

mm/usercopy: Use memory range to be accessed for wraparound check



Currently, when checking to see if accessing n bytes starting at
address "ptr" will cause a wraparound in the memory addresses,
the check in check_bogus_address() adds an extra byte, which is
incorrect, as the range of addresses that will be accessed is
[ptr, ptr + (n - 1)].

This can lead to incorrectly detecting a wraparound in the
memory address, when trying to read 4 KB from memory that is
mapped to the the last possible page in the virtual address
space, when in fact, accessing that range of memory would not
cause a wraparound to occur.

Use the memory range that will actually be accessed when
considering if accessing a certain amount of bytes will cause
the memory address to wrap around.

Change-Id: Ie71a5a5cb9f6dc15d82a77202b4aaa775eb549f7
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>

parent 71f9600f

mm/usercopy.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -151,7 +151,7 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n,
		bool to_user)
		{
		/* Reject if object wraps past end of memory. */
		if (ptr + n < ptr)
		if (ptr + (n - 1) < ptr)
		usercopy_abort("wrapped address", NULL, to_user, 0, ptr + n);

		/* Reject if NULL or ZERO-allocation. */