| Message ID | 20201130100425.GB2789@kadam (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] net/x25: prevent a couple of overflows | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | fail | Series targets non-next tree, but doesn't contain any Fixes tags |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for net |
| netdev/subject_prefix | success | Link |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 15 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
| netdev/stable | success | Stable not CCed |
On 2020-11-30 11:04, Dan Carpenter wrote: > From: "kiyin(尹亮)" <kiyin@tencent.com> > > The .x25_addr[] address comes from the user and is not necessarily > NUL terminated. This leads to a couple problems. The first problem is > that the strlen() in x25_bind() can read beyond the end of the buffer. > > The second problem is more subtle and could result in memory > corruption. > The call tree is: > x25_connect() > --> x25_write_internal() > --> x25_addr_aton() > > The .x25_addr[] buffers are copied to the "addresses" buffer from > x25_write_internal() so it will lead to stack corruption. > > The x25 protocol only allows 15 character addresses so putting a NUL > terminator as the 16th character is safe and obviously preferable to > reading out of bounds. > OK, I see the potential danger. I'm just wondering what is the better approach here to counteract it: 1. check if the string is terminated or exceeds the maximum allowed length and report an error if necessary. 2. always terminate the string at byte 15 as you suggested. > Signed-off-by: "kiyin(尹亮)" <kiyin@tencent.com> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> > --- > > net/x25/af_x25.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c > index 0bbb283f23c9..3180f15942fe 100644 > --- a/net/x25/af_x25.c > +++ b/net/x25/af_x25.c > @@ -686,6 +686,8 @@ static int x25_bind(struct socket *sock, struct > sockaddr *uaddr, int addr_len) > goto out; > } > > + addr->sx25_addr.x25_addr[X25_ADDR_LEN - 1] = '\0'; > + > /* check for the null_x25_address */ > if (strcmp(addr->sx25_addr.x25_addr, null_x25_address.x25_addr)) { > > @@ -779,6 +781,7 @@ static int x25_connect(struct socket *sock, struct > sockaddr *uaddr, > goto out; > > rc = -ENETUNREACH; > + addr->sx25_addr.x25_addr[X25_ADDR_LEN - 1] = '\0'; > rt = x25_get_route(&addr->sx25_addr); > if (!rt) > goto out;
diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c index 0bbb283f23c9..3180f15942fe 100644 --- a/net/x25/af_x25.c +++ b/net/x25/af_x25.c @@ -686,6 +686,8 @@ static int x25_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) goto out; } + addr->sx25_addr.x25_addr[X25_ADDR_LEN - 1] = '\0'; + /* check for the null_x25_address */ if (strcmp(addr->sx25_addr.x25_addr, null_x25_address.x25_addr)) { @@ -779,6 +781,7 @@ static int x25_connect(struct socket *sock, struct sockaddr *uaddr, goto out; rc = -ENETUNREACH; + addr->sx25_addr.x25_addr[X25_ADDR_LEN - 1] = '\0'; rt = x25_get_route(&addr->sx25_addr); if (!rt) goto out;