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Commit 778959db authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Linus Torvalds
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[PATCH] s390: ptrace peek and poke 



The special cases of peek and poke on acrs[15] and the fpc register are not
handled correctly.  A poke on acrs[15] will clobber the 4 bytes after the
access registers in the thread_info structure.  That happens to be the kernel
stack pointer.  A poke on the fpc with an invalid value is not caught by the
validity check.  On the next context switch the broken fpc value will cause a
program check in the kernel.  Improving the checks in peek and poke fixes
this.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 854715be

arch/s390/kernel/ptrace.c

+43 −5
Original line number Diff line number Diff line
@@ -40,6 +40,7 @@ 
#include <asm/pgalloc.h>

#include <asm/system.h>

#include <asm/uaccess.h>

#include <asm/unistd.h>



#ifdef CONFIG_S390_SUPPORT

#include "compat_ptrace.h"
@@ -130,13 +131,19 @@ static int 
peek_user(struct task_struct *child, addr_t addr, addr_t data)

{

	struct user *dummy = NULL;

	addr_t offset, tmp;

	addr_t offset, tmp, mask;



	/*

	 * Stupid gdb peeks/pokes the access registers in 64 bit with

	 * an alignment of 4. Programmers from hell...

	 */

	if ((addr & 3) || addr > sizeof(struct user) - __ADDR_MASK)

	mask = __ADDR_MASK;

#ifdef CONFIG_ARCH_S390X

	if (addr >= (addr_t) &dummy->regs.acrs &&

	    addr < (addr_t) &dummy->regs.orig_gpr2)

		mask = 3;

#endif

	if ((addr & mask) || addr > sizeof(struct user) - __ADDR_MASK)

		return -EIO;



	if (addr < (addr_t) &dummy->regs.acrs) {
@@ -153,6 +160,16 @@ peek_user(struct task_struct *child, addr_t addr, addr_t data) 
		 * access registers are stored in the thread structure

		 */

		offset = addr - (addr_t) &dummy->regs.acrs;

#ifdef CONFIG_ARCH_S390X

		/*

		 * Very special case: old & broken 64 bit gdb reading

		 * from acrs[15]. Result is a 64 bit value. Read the

		 * 32 bit acrs[15] value and shift it by 32. Sick...

		 */

		if (addr == (addr_t) &dummy->regs.acrs[15])

			tmp = ((unsigned long) child->thread.acrs[15]) << 32;

		else

#endif

		tmp = *(addr_t *)((addr_t) &child->thread.acrs + offset);



	} else if (addr == (addr_t) &dummy->regs.orig_gpr2) {
@@ -167,6 +184,9 @@ peek_user(struct task_struct *child, addr_t addr, addr_t data) 
		 */

		offset = addr - (addr_t) &dummy->regs.fp_regs;

		tmp = *(addr_t *)((addr_t) &child->thread.fp_regs + offset);

		if (addr == (addr_t) &dummy->regs.fp_regs.fpc)

			tmp &= (unsigned long) FPC_VALID_MASK

				<< (BITS_PER_LONG - 32);



	} else if (addr < (addr_t) (&dummy->regs.per_info + 1)) {

		/*
@@ -191,13 +211,19 @@ static int 
poke_user(struct task_struct *child, addr_t addr, addr_t data)

{

	struct user *dummy = NULL;

	addr_t offset;

	addr_t offset, mask;



	/*

	 * Stupid gdb peeks/pokes the access registers in 64 bit with

	 * an alignment of 4. Programmers from hell indeed...

	 */

	if ((addr & 3) || addr > sizeof(struct user) - __ADDR_MASK)

	mask = __ADDR_MASK;

#ifdef CONFIG_ARCH_S390X

	if (addr >= (addr_t) &dummy->regs.acrs &&

	    addr < (addr_t) &dummy->regs.orig_gpr2)

		mask = 3;

#endif

	if ((addr & mask) || addr > sizeof(struct user) - __ADDR_MASK)

		return -EIO;



	if (addr < (addr_t) &dummy->regs.acrs) {
@@ -224,6 +250,17 @@ poke_user(struct task_struct *child, addr_t addr, addr_t data) 
		 * access registers are stored in the thread structure

		 */

		offset = addr - (addr_t) &dummy->regs.acrs;

#ifdef CONFIG_ARCH_S390X

		/*

		 * Very special case: old & broken 64 bit gdb writing

		 * to acrs[15] with a 64 bit value. Ignore the lower

		 * half of the value and write the upper 32 bit to

		 * acrs[15]. Sick...

		 */

		if (addr == (addr_t) &dummy->regs.acrs[15])

			child->thread.acrs[15] = (unsigned int) (data >> 32);

		else

#endif

		*(addr_t *)((addr_t) &child->thread.acrs + offset) = data;



	} else if (addr == (addr_t) &dummy->regs.orig_gpr2) {
@@ -237,7 +274,8 @@ poke_user(struct task_struct *child, addr_t addr, addr_t data) 
		 * floating point regs. are stored in the thread structure

		 */

		if (addr == (addr_t) &dummy->regs.fp_regs.fpc &&

		    (data & ~FPC_VALID_MASK) != 0)

		    (data & ~((unsigned long) FPC_VALID_MASK

			      << (BITS_PER_LONG - 32))) != 0)

			return -EINVAL;

		offset = addr - (addr_t) &dummy->regs.fp_regs;

		*(addr_t *)((addr_t) &child->thread.fp_regs + offset) = data;