Re: [libvirt] [PATCH] Allocate buffer to hold xend response
Jim Fehlig wrote:
Eric Blake wrote:
>> BTW, I pushed the patch after Eric's ACK. I'll role another to address
>> these issues, once I get confirmation on the NUL-termination.
>
> Looking forward to the followup, and thanks for Jim for catching
> something I missed in my ACK (even if we didn't catch it in time).
Patch that includes Jim's suggestions ...
...
Subject: [PATCH] Fixes for commit 211dd1e9
Fixes for issues in commit 211dd1e9 noted by by Jim Meyering.
1. Allocate content buffer of size content_length + 1 to ensure
NUL-termination.
2. Limit content buffer size to 64k
3. Fix whitespace issue
---
src/xen/xend_internal.c | 14 ++++++++++++--
1 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/src/xen/xend_internal.c b/src/xen/xend_internal.c
index 0c1a738..3b9da6b 100644
--- a/src/xen/xend_internal.c
+++ b/src/xen/xend_internal.c
@@ -68,6 +68,7 @@
# define XEND_CONFIG_MIN_VERS_PVFB_NEWCONF 3
#endif
+#define XEND_RCV_BUF_MAX_LEN 65536
#ifndef PROXY
static int
@@ -330,7 +331,16 @@ xend_req(int fd, char **content)
if (content_length > 0) {
ssize_t ret;
Hi Jim,
Thanks for adding that.
This part looks fine.
- if (VIR_ALLOC_N(*content, content_length) < 0 ) {
+ if (content_length > XEND_RCV_BUF_MAX_LEN) {
+ virXendError(VIR_ERR_INTERNAL_ERROR,
+ _("Xend returned HTTP Content-Length of %d, "
+ "which exceeds maximum of %d"),
+ content_length,
+ XEND_RCV_BUF_MAX_LEN);
+ return -1;
+ }
+
This is subtle enough that a comment might avoid trouble later.
/* Allocate one byte beyond the end of the largest buffer we will read.
Combined with the fact that VIR_ALLOC_N zeros the returned buffer,
this guarantees that "content" will always be NUL-terminated. */
+ if (VIR_ALLOC_N(*content, content_length + 1) < 0 ) {
virReportOOMError();
return -1;
}
@@ -380,7 +390,7 @@ xend_get(virConnectPtr xend, const char *path,
virXendError(VIR_ERR_GET_FAILED,
_("%d status from xen daemon: %s:%s"),
ret, path,
- content ? *content: "NULL");
+ content ? *content : "NULL");
Oh! I've just noticed that testing "content" is wrong,
since it will always be non-NULL. BTW, the parameter should
be marked as such via "ATTRIBUTE_NONNULL (3)".
The test should examine "*content", i.e.,
*content ? *content : "NULL");
Then I remembered the NULLSTR macro.
You can replace the above with this:
NULLSTR(*content));
FYI, here's its definition:
$ git grep -A2 ine.NULLSTR
src/internal.h:# define NULLSTR(s) \
src/internal.h- ((void)verify_true(sizeof *(s) == sizeof (char)), \
src/internal.h- (s) ? (s) : "(null)")