From: Martin Schwidefsky <[email protected]>
[S390] user readable uninitialised kernel memory.
A user space program can read uninitialised kernel memory
by appending to a file from a bad address and then reading
the result back. The cause is the copy_from_user function
that does not clear the remaining bytes of the kernel
buffer after it got a fault on the user space address.
Signed-off-by: Martin Schwidefsky <[email protected]>
---
arch/s390/lib/uaccess_mvcos.c | 22 ++++++++++++++++------
arch/s390/lib/uaccess_std.c | 36 ++++++++++++++++++++++++++----------
2 files changed, 42 insertions(+), 16 deletions(-)
diff -urpN linux-2.6/arch/s390/lib/uaccess_mvcos.c linux-2.6-patched/arch/s390/lib/uaccess_mvcos.c
--- linux-2.6/arch/s390/lib/uaccess_mvcos.c 2006-09-28 14:58:39.000000000 +0200
+++ linux-2.6-patched/arch/s390/lib/uaccess_mvcos.c 2006-09-28 14:58:57.000000000 +0200
@@ -35,7 +35,7 @@ size_t copy_from_user_mvcos(size_t size,
tmp1 = -4096UL;
asm volatile(
"0: .insn ss,0xc80000000000,0(%0,%2),0(%1),0\n"
- " jz 4f\n"
+ " jz 7f\n"
"1:"ALR" %0,%3\n"
" "SLR" %1,%3\n"
" "SLR" %2,%3\n"
@@ -44,13 +44,23 @@ size_t copy_from_user_mvcos(size_t size,
" nr %4,%3\n" /* %4 = (ptr + 4095) & -4096 */
" "SLR" %4,%1\n"
" "CLR" %0,%4\n" /* copy crosses next page boundary? */
- " jnh 5f\n"
+ " jnh 4f\n"
"3: .insn ss,0xc80000000000,0(%4,%2),0(%1),0\n"
" "SLR" %0,%4\n"
- " j 5f\n"
- "4:"SLR" %0,%0\n"
- "5: \n"
- EX_TABLE(0b,2b) EX_TABLE(3b,5b)
+ " "ALR" %2,%4\n"
+ "4:"LHI" %4,-1\n"
+ " "ALR" %4,%0\n" /* copy remaining size, subtract 1 */
+ " bras %3,6f\n" /* memset loop */
+ " xc 0(1,%2),0(%2)\n"
+ "5: xc 0(256,%2),0(%2)\n"
+ " la %2,256(%2)\n"
+ "6:"AHI" %4,-256\n"
+ " jnm 5b\n"
+ " ex %4,0(%3)\n"
+ " j 8f\n"
+ "7:"SLR" %0,%0\n"
+ "8: \n"
+ EX_TABLE(0b,2b) EX_TABLE(3b,4b)
: "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
: "d" (reg0) : "cc", "memory");
return size;
diff -urpN linux-2.6/arch/s390/lib/uaccess_std.c linux-2.6-patched/arch/s390/lib/uaccess_std.c
--- linux-2.6/arch/s390/lib/uaccess_std.c 2006-09-28 14:58:39.000000000 +0200
+++ linux-2.6-patched/arch/s390/lib/uaccess_std.c 2006-09-28 14:58:57.000000000 +0200
@@ -35,25 +35,35 @@ size_t copy_from_user_std(size_t size, c
tmp1 = -256UL;
asm volatile(
"0: mvcp 0(%0,%2),0(%1),%3\n"
- " jz 5f\n"
+ " jz 8f\n"
"1:"ALR" %0,%3\n"
" la %1,256(%1)\n"
" la %2,256(%2)\n"
"2: mvcp 0(%0,%2),0(%1),%3\n"
" jnz 1b\n"
- " j 5f\n"
+ " j 8f\n"
"3: la %4,255(%1)\n" /* %4 = ptr + 255 */
" "LHI" %3,-4096\n"
" nr %4,%3\n" /* %4 = (ptr + 255) & -4096 */
" "SLR" %4,%1\n"
" "CLR" %0,%4\n" /* copy crosses next page boundary? */
- " jnh 6f\n"
+ " jnh 5f\n"
"4: mvcp 0(%4,%2),0(%1),%3\n"
" "SLR" %0,%4\n"
- " j 6f\n"
- "5:"SLR" %0,%0\n"
- "6: \n"
- EX_TABLE(0b,3b) EX_TABLE(2b,3b) EX_TABLE(4b,6b)
+ " "ALR" %2,%4\n"
+ "5:"LHI" %4,-1\n"
+ " "ALR" %4,%0\n" /* copy remaining size, subtract 1 */
+ " bras %3,7f\n" /* memset loop */
+ " xc 0(1,%2),0(%2)\n"
+ "6: xc 0(256,%2),0(%2)\n"
+ " la %2,256(%2)\n"
+ "7:"AHI" %4,-256\n"
+ " jnm 6b\n"
+ " ex %4,0(%3)\n"
+ " j 9f\n"
+ "8:"SLR" %0,%0\n"
+ "9: \n"
+ EX_TABLE(0b,3b) EX_TABLE(2b,3b) EX_TABLE(4b,5b)
: "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
: : "cc", "memory");
return size;
@@ -67,16 +77,22 @@ size_t copy_from_user_std_small(size_t s
asm volatile(
"0: mvcp 0(%0,%2),0(%1),%3\n"
" "SLR" %0,%0\n"
- " j 3f\n"
+ " j 5f\n"
"1: la %4,255(%1)\n" /* %4 = ptr + 255 */
" "LHI" %3,-4096\n"
" nr %4,%3\n" /* %4 = (ptr + 255) & -4096 */
" "SLR" %4,%1\n"
" "CLR" %0,%4\n" /* copy crosses next page boundary? */
- " jnh 3f\n"
+ " jnh 5f\n"
"2: mvcp 0(%4,%2),0(%1),%3\n"
" "SLR" %0,%4\n"
- "3:\n"
+ " "ALR" %2,%4\n"
+ "3:"LHI" %4,-1\n"
+ " "ALR" %4,%0\n" /* copy remaining size, subtract 1 */
+ " bras %3,4f\n"
+ " xc 0(1,%2),0(%2)\n"
+ "4: ex %4,0(%3)\n"
+ "5:\n"
EX_TABLE(0b,1b) EX_TABLE(2b,3b)
: "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
: : "cc", "memory");