* [PATCH] fix double-fetch bug in sock_getsockopt()
@ 2019-06-13 10:44 JingYi Hou
2019-06-15 20:32 ` David Miller
0 siblings, 1 reply; 2+ messages in thread
From: JingYi Hou @ 2019-06-13 10:44 UTC (permalink / raw)
To: davem; +Cc: netdev, linux-kernel
In sock_getsockopt(), 'optlen' is fetched the first time from userspace.
'len < 0' is then checked. Then in condition 'SO_MEMINFO', 'optlen' is
fetched the second time from userspace without check.
if a malicious user can change it between two fetches may cause security
problems or unexpected behaivor.
To fix this, we need to recheck it in the second fetch.
Signed-off-by: JingYi Hou <houjingyi647@gmail.com>
---
net/core/sock.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/core/sock.c b/net/core/sock.c
index 2b3701958486..577780c935ee 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1479,6 +1479,8 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
if (get_user(len, optlen))
return -EFAULT;
+ if (len < 0)
+ return -EINVAL;
sk_get_meminfo(sk, meminfo);
--
2.20.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] fix double-fetch bug in sock_getsockopt()
2019-06-13 10:44 [PATCH] fix double-fetch bug in sock_getsockopt() JingYi Hou
@ 2019-06-15 20:32 ` David Miller
0 siblings, 0 replies; 2+ messages in thread
From: David Miller @ 2019-06-15 20:32 UTC (permalink / raw)
To: houjingyi647; +Cc: netdev, linux-kernel
From: JingYi Hou <houjingyi647@gmail.com>
Date: Thu, 13 Jun 2019 18:44:57 +0800
> In sock_getsockopt(), 'optlen' is fetched the first time from userspace.
> 'len < 0' is then checked. Then in condition 'SO_MEMINFO', 'optlen' is
> fetched the second time from userspace without check.
>
> if a malicious user can change it between two fetches may cause security
> problems or unexpected behaivor.
>
> To fix this, we need to recheck it in the second fetch.
>
> Signed-off-by: JingYi Hou <houjingyi647@gmail.com>
THere is no reason to fetch len a second time, so please just remove
the get_user() call here instead.
Also, please format your Subject line properly with appropriate subsystem
prefixes etc.
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2019-06-13 10:44 [PATCH] fix double-fetch bug in sock_getsockopt() JingYi Hou
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