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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: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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commit 778959db97c7ed8eed4025916916b17a4629ce3d 1 parent 854715b
Martin Schwidefsky authored Linus Torvalds committed
Showing with 43 additions and 5 deletions.
  1. +43 −5 arch/s390/kernel/ptrace.c
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48 arch/s390/kernel/ptrace.c
@@ -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;
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