On 04/11/2021 07:04 PM, Jinyang He wrote:
Commit 04324f44cb69 ("MIPS: Remove get_fs/set_fs") brought a problem for
strnlen_user(). Jump out when checking access_ok() with condition that
(s + strlen(s)) < __UA_LIMIT <= (s + n). The old __strnlen_user_asm()
just checked (ua_limit & s) without checking (ua_limit & (s + n)).
Therefore, find strlen form s to __UA_LIMIT - 1 in that condition.
Signed-off-by: Jinyang He <hejinyang@xxxxxxxxxxx>
---
arch/mips/include/asm/uaccess.h | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h
index 91bc7fb..85ba0c8 100644
--- a/arch/mips/include/asm/uaccess.h
+++ b/arch/mips/include/asm/uaccess.h
@@ -630,8 +630,15 @@ static inline long strnlen_user(const char __user *s, long n)
{
long res;
- if (!access_ok(s, n))
- return -0;
+ if (unlikely(n <= 0))
+ return 0;
+
+ if (!access_ok(s, n)) {
+ if (!access_ok(s, 0))
+ return 0;
+
+ n = __UA_LIMIT - (unsigned long)s - 1;
+ }
might_fault();
__asm__ __volatile__(
The following simple changes are OK to fix this issue?
diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h
index 91bc7fb..eafc99b 100644
--- a/arch/mips/include/asm/uaccess.h
+++ b/arch/mips/include/asm/uaccess.h
@@ -630,8 +630,8 @@ static inline long strnlen_user(const char __user *s, long n)
{
long res;
- if (!access_ok(s, n))
- return -0;
+ if (!access_ok(s, 1))
+ return 0;
might_fault();
__asm__ __volatile__(
Thanks,
Tiezhu
