Commit 52149ba6 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

[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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 51dced54

arch/s390/lib/uaccess_mvcos.c

+16 −6
Original line number Diff line number Diff line
@@ -35,7 +35,7 @@ size_t copy_from_user_mvcos(size_t size, const void __user *ptr, void *x) 
	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, const void __user *ptr, void *x) 
		"   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;

arch/s390/lib/uaccess_std.c

+26 −10
Original line number Diff line number Diff line
@@ -35,25 +35,35 @@ size_t copy_from_user_std(size_t size, const void __user *ptr, void *x) 
	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 size, const void __user *ptr, void *x) 
	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");

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