Commit 9ba4ace3 authored Jun 20, 2007 by Segher Boessenkool Committed by Paul Mackerras Jun 20, 2007

[POWERPC] PowerPC: Prevent data exception in kernel space (32-bit)



The "is_exec" branch of the protection check in do_page_fault()
didn't do anything on 32-bit PowerPC.  So if a userland program
jumps to a page with Linux protection flags "---p", all the tests
happily fall through, and handle_mm_fault() is called, which in
turn calls handle_pte_fault(), which calls update_mmu_cache(),
which goes flush the dcache to a page with no access rights.

Boom.

This fixes it.

Signed-off-by: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>

parent 7c8545e9

arch/powerpc/mm/fault.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -279,14 +279,13 @@ good_area:
		#endif /* CONFIG_8xx */

		if (is_exec) {
		#ifdef CONFIG_PPC64
		#if !(defined(CONFIG_4xx) \|\| defined(CONFIG_BOOKE))
		/* protection fault */
		if (error_code & DSISR_PROTFAULT)
		goto bad_area;
		if (!(vma->vm_flags & VM_EXEC))
		goto bad_area;
		#endif
		#if defined(CONFIG_4xx) \|\| defined(CONFIG_BOOKE)
		#else
		pte_t *ptep;
		pmd_t *pmdp;

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