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[S390] user readable uninitialised kernel memory.

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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 <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky
2006-09-28 16:56:03 +02:00
parent 51dced544e
commit 52149ba6b0
2 changed files with 42 additions and 16 deletions
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22
arch/s390/lib/uaccess_mvcos.c
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@@ -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;