Merge tag 'pull-9p-20230608' of https://github.com/cschoenebeck/qemu into staging

* Fix for CVE-2023-2861.

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# gpg: Signature made Thu 08 Jun 2023 08:09:23 AM PDT
# gpg:                using RSA key 96D8D110CF7AF8084F88590134C2B58765A47395
# gpg:                issuer "qemu_oss@crudebyte.com"
# gpg: Good signature from "Christian Schoenebeck <qemu_oss@crudebyte.com>" [unknown]
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: ECAB 1A45 4014 1413 BA38  4926 30DB 47C3 A012 D5F4
#      Subkey fingerprint: 96D8 D110 CF7A F808 4F88  5901 34C2 B587 65A4 7395

* tag 'pull-9p-20230608' of https://github.com/cschoenebeck/qemu:
  9pfs: prevent opening special files (CVE-2023-2861)

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 25 insertions, 2 deletions

diff --git a/fsdev/virtfs-proxy-helper.c b/fsdev/virtfs-proxy-helper.c
index 5cafcd7703..d9511f429c 100644
--- a/fsdev/virtfs-proxy-helper.c
+++ b/fsdev/virtfs-proxy-helper.c
@@ -26,6 +26,7 @@
 #include "qemu/xattr.h"
 #include "9p-iov-marshal.h"
 #include "hw/9pfs/9p-proxy.h"
+#include "hw/9pfs/9p-util.h"
 #include "fsdev/9p-iov-marshal.h"
 
 #define PROGNAME "virtfs-proxy-helper"
@@ -339,6 +340,28 @@ static void resetugid(int suid, int sgid)
 }
 
 /*
+ * Open regular file or directory. Attempts to open any special file are
+ * rejected.
+ *
+ * returns file descriptor or -1 on error
+ */
+static int open_regular(const char *pathname, int flags, mode_t mode)
+{
+    int fd;
+
+    fd = open(pathname, flags, mode);
+    if (fd < 0) {
+        return fd;
+    }
+
+    if (close_if_special_file(fd) < 0) {
+        return -1;
+    }
+
+    return fd;
+}
+
+/*
  * send response in two parts
  * 1) ProxyHeader
  * 2) Response or error status
@@ -682,7 +705,7 @@ static int do_create(struct iovec *iovec)
     if (ret < 0) {
         goto unmarshal_err_out;
     }
-    ret = open(path.data, flags, mode);
+    ret = open_regular(path.data, flags, mode);
     if (ret < 0) {
         ret = -errno;
     }
@@ -707,7 +730,7 @@ static int do_open(struct iovec *iovec)
     if (ret < 0) {
         goto err_out;
     }
-    ret = open(path.data, flags);
+    ret = open_regular(path.data, flags, 0);
     if (ret < 0) {
         ret = -errno;
     }