Commit f45655f6 authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky

s390/uaccess: fix strncpy_from_user/strnlen_user zero maxlen case

If the maximum length specified for the to be accessed string for
strncpy_from_user() and strnlen_user() is zero the following incorrect
values would be returned or incorrect memory accesses would happen:

strnlen_user_std() and strnlen_user_pt() incorrectly return "1"
strncpy_from_user_pt() would incorrectly access "dst[maxlen - 1]"
strncpy_from_user_mvcos() would incorrectly return "-EFAULT"

Fix all these oddities by adding early checks.
Reviewed-by: default avatarGerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent d7b788cd
...@@ -184,6 +184,8 @@ static size_t strncpy_from_user_mvcos(size_t count, const char __user *src, ...@@ -184,6 +184,8 @@ static size_t strncpy_from_user_mvcos(size_t count, const char __user *src,
{ {
size_t done, len, offset, len_str; size_t done, len, offset, len_str;
if (unlikely(!count))
return 0;
done = 0; done = 0;
do { do {
offset = (size_t)src & ~PAGE_MASK; offset = (size_t)src & ~PAGE_MASK;
......
...@@ -172,6 +172,8 @@ static size_t strnlen_user_pt(size_t count, const char __user *src) ...@@ -172,6 +172,8 @@ static size_t strnlen_user_pt(size_t count, const char __user *src)
unsigned long offset, done, len, kaddr; unsigned long offset, done, len, kaddr;
size_t len_str; size_t len_str;
if (unlikely(!count))
return 0;
if (segment_eq(get_fs(), KERNEL_DS)) if (segment_eq(get_fs(), KERNEL_DS))
return strnlen((const char __kernel __force *) src, count) + 1; return strnlen((const char __kernel __force *) src, count) + 1;
done = 0; done = 0;
...@@ -202,6 +204,8 @@ static size_t strncpy_from_user_pt(size_t count, const char __user *src, ...@@ -202,6 +204,8 @@ static size_t strncpy_from_user_pt(size_t count, const char __user *src,
{ {
size_t n = strnlen_user_pt(count, src); size_t n = strnlen_user_pt(count, src);
if (unlikely(!count))
return 0;
if (!n) if (!n)
return -EFAULT; return -EFAULT;
if (n > count) if (n > count)
......
...@@ -188,6 +188,8 @@ size_t strnlen_user_std(size_t size, const char __user *src) ...@@ -188,6 +188,8 @@ size_t strnlen_user_std(size_t size, const char __user *src)
register unsigned long reg0 asm("0") = 0UL; register unsigned long reg0 asm("0") = 0UL;
unsigned long tmp1, tmp2; unsigned long tmp1, tmp2;
if (unlikely(!size))
return 0;
asm volatile( asm volatile(
" la %2,0(%1)\n" " la %2,0(%1)\n"
" la %3,0(%0,%1)\n" " la %3,0(%0,%1)\n"
......
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