[Libguestfs] [PATCH v2] Daemon: fix handling of errors from xread and xwrite.
Richard W.M. Jones
rjones at redhat.com
Thu Sep 17 14:50:01 UTC 2009
On Thu, Sep 17, 2009 at 03:39:45PM +0100, Daniel P. Berrange wrote:
> On Thu, Sep 17, 2009 at 03:33:24PM +0100, Richard W.M. Jones wrote:
> >
> > This caused me to waste about 3 hours looking for a non-existent "data
> > corrupter" bug, which turned out to be the result of not checking the
> > return value of xread ...
>
> You might want to add
>
> __attribute__((__warn_unused_result__))
>
> to the header file decl of xread/xwrite so that the compiler will
> warn if any other code areas forget to check the return error code
Good idea. Updated patch attached.
Rich.
--
Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones
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-------------- next part --------------
>From af93e24c91d5448b34a7dcb0355b904516d531fc Mon Sep 17 00:00:00 2001
From: Richard Jones <rjones at trick.home.annexia.org>
Date: Thu, 17 Sep 2009 15:28:41 +0100
Subject: [PATCH 1/3] Daemon: fix handling of errors from xread and xwrite.
If xread or xwrite returns -1, that indicates an error and we
should exit. Note that xread/xwrite has already printed the
error message.
---
daemon/daemon.h | 6 ++++--
daemon/guestfsd.c | 3 ++-
daemon/proto.c | 18 +++++++++++-------
3 files changed, 17 insertions(+), 10 deletions(-)
diff --git a/daemon/daemon.h b/daemon/daemon.h
index 83c9672..86c6876 100644
--- a/daemon/daemon.h
+++ b/daemon/daemon.h
@@ -36,8 +36,10 @@ extern int sysroot_len;
extern char *sysroot_path (const char *path);
-extern int xwrite (int sock, const void *buf, size_t len);
-extern int xread (int sock, void *buf, size_t len);
+extern int xwrite (int sock, const void *buf, size_t len)
+ __attribute__((__warn_unused_result__));
+extern int xread (int sock, void *buf, size_t len)
+ __attribute__((__warn_unused_result__));
extern int add_string (char ***argv, int *size, int *alloc, const char *str);
extern int count_strings (char *const *argv);
diff --git a/daemon/guestfsd.c b/daemon/guestfsd.c
index ebaf960..bfd8139 100644
--- a/daemon/guestfsd.c
+++ b/daemon/guestfsd.c
@@ -197,7 +197,8 @@ main (int argc, char *argv[])
exit (1);
}
- (void) xwrite (sock, buf, xdr_getpos (&xdr));
+ if (xwrite (sock, buf, xdr_getpos (&xdr)) == -1)
+ exit (1);
xdr_destroy (&xdr);
diff --git a/daemon/proto.c b/daemon/proto.c
index 817a995..037a9e0 100644
--- a/daemon/proto.c
+++ b/daemon/proto.c
@@ -62,7 +62,9 @@ main_loop (int _sock)
#endif
/* Read the length word. */
- xread (sock, lenbuf, 4);
+ if (xread (sock, lenbuf, 4) == -1)
+ exit (1);
+
xdrmem_create (&xdr, lenbuf, 4, XDR_DECODE);
xdr_uint32_t (&xdr, &len);
xdr_destroy (&xdr);
@@ -79,7 +81,8 @@ main_loop (int _sock)
continue;
}
- xread (sock, buf, len);
+ if (xread (sock, buf, len) == -1)
+ exit (1);
#if 0
if (verbose) {
@@ -307,7 +310,9 @@ receive_file (receive_cb cb, void *opaque)
for (;;) {
/* Read the length word. */
- xread (sock, lenbuf, 4);
+ if (xread (sock, lenbuf, 4) == -1)
+ exit (1);
+
xdrmem_create (&xdr, lenbuf, 4, XDR_DECODE);
xdr_uint32_t (&xdr, &len);
xdr_destroy (&xdr);
@@ -327,7 +332,8 @@ receive_file (receive_cb cb, void *opaque)
return -1;
}
- xread (sock, buf, len);
+ if (xread (sock, buf, len) == -1)
+ exit (1);
xdrmem_create (&xdr, buf, len, XDR_DECODE);
memset (&chunk, 0, sizeof chunk);
@@ -444,10 +450,8 @@ check_for_library_cancellation (void)
/* Read the message from the daemon. */
r = xread (sock, buf, sizeof buf);
- if (r == -1) {
- perror ("read");
+ if (r == -1)
return 0;
- }
xdrmem_create (&xdr, buf, sizeof buf, XDR_DECODE);
xdr_uint32_t (&xdr, &flag);
--
1.6.2.5
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