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lkdtm: Prevent the compiler from optimising lkdtm_CORRUPT_STACK()

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At least on powerpc with GCC 6, the compiler is smart enough to optimise
lkdtm_CORRUPT_STACK() into an empty function that just returns.

If we print the buffer after we've written to it that prevents the
compiler from optimising away data and the memset().

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Michael Ellerman 2016-11-15 18:02:32 +11:00 committed by Greg Kroah-Hartman
parent 967b274e02
commit c55d240003
1 changed files with 2 additions and 1 deletions
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3
drivers/misc/lkdtm_bugs.c
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@ -80,7 +80,8 @@ noinline void lkdtm_CORRUPT_STACK(void)
/* Use default char array length that triggers stack protection. */ /* Use default char array length that triggers stack protection. */
char data[8]; char data[8];
memset((void *)data, 0, 64); memset((void *)data, 'a', 64);
pr_info("Corrupted stack with '%16s'...\n", data);
} }
void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void) void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void)