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

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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>
This commit is contained in:
Isaac J. Manjarres 2018-11-01 12:57:27 -07:00 committed by Gerrit - the friendly Code Review server
parent 479064846b
commit c7f07455e3
1 changed files with 1 additions and 1 deletions
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2
mm/usercopy.c
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@ -121,7 +121,7 @@ static inline const char *check_kernel_text_object(const void *ptr,
static inline const char *check_bogus_address(const void *ptr, unsigned long n)
{
/* Reject if object wraps past end of memory. */
if ((unsigned long)ptr + n < (unsigned long)ptr)
if ((unsigned long)ptr + (n - 1) < (unsigned long)ptr)
return "<wrapped address>";
/* Reject if NULL or ZERO-allocation. */