Messages in this thread Patch in this message | | | Subject | [patch 4/8] uml: disallow stack access below $esp like i386 / x86_64 [before 2.6.11] | From | blaisorblade@yahoo ... | Date | Fri, 04 Feb 2005 19:35:48 +0100 |
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From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
When a page fault occurs on an address below the stack-vma, UML tries to expand the stack. On i386 and x86_64, the failing address is compared to the current userspace stack pointer. If the failing address is below "esp-32" resp. "rsp-128", stack expansion is not allowed, and a SIGSEGV is given to the user. This patch makes UML behave like i386/x86_64.
Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com> Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> ---
linux-2.6.11-paolo/arch/um/kernel/trap_kern.c | 2 ++ linux-2.6.11-paolo/include/asm-um/processor-i386.h | 3 +++ linux-2.6.11-paolo/include/asm-um/processor-x86_64.h | 3 +++ 3 files changed, 8 insertions(+)
diff -puN arch/um/kernel/trap_kern.c~uml-stack-expansion arch/um/kernel/trap_kern.c --- linux-2.6.11/arch/um/kernel/trap_kern.c~uml-stack-expansion 2005-02-04 06:18:18.689557088 +0100 +++ linux-2.6.11-paolo/arch/um/kernel/trap_kern.c 2005-02-04 06:18:18.739549488 +0100 @@ -48,6 +48,8 @@ int handle_page_fault(unsigned long addr goto good_area; else if(!(vma->vm_flags & VM_GROWSDOWN)) goto out; + else if(!ARCH_IS_STACKGROW(address)) + goto out; else if(expand_stack(vma, address)) goto out; diff -puN include/asm-um/processor-i386.h~uml-stack-expansion include/asm-um/processor-i386.h --- linux-2.6.11/include/asm-um/processor-i386.h~uml-stack-expansion 2005-02-04 06:18:18.726551464 +0100 +++ linux-2.6.11-paolo/include/asm-um/processor-i386.h 2005-02-04 06:18:18.739549488 +0100 @@ -27,6 +27,9 @@ struct arch_thread { #define current_text_addr() \ ({ void *pc; __asm__("movl $1f,%0\n1:":"=g" (pc)); pc; }) +#define ARCH_IS_STACKGROW(address) \ + (address + 32 >= UPT_SP(¤t->thread.regs.regs)) + #include "asm/processor-generic.h" #endif diff -puN include/asm-um/processor-x86_64.h~uml-stack-expansion include/asm-um/processor-x86_64.h --- linux-2.6.11/include/asm-um/processor-x86_64.h~uml-stack-expansion 2005-02-04 06:18:18.736549944 +0100 +++ linux-2.6.11-paolo/include/asm-um/processor-x86_64.h 2005-02-04 06:18:18.740549336 +0100 @@ -17,6 +17,9 @@ struct arch_thread { #define current_text_addr() \ ({ void *pc; __asm__("movq $1f,%0\n1:":"=g" (pc)); pc; }) +#define ARCH_IS_STACKGROW(address) \ + (address + 128 >= UPT_SP(¤t->thread.regs.regs)) + #include "asm/processor-generic.h" #endif _ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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