[libvirt] [PATCH] conf: fix use after free in virChrdevOpen

[Ján Tomko]

Don't free the stream on error if we've successfully added it
to the hash table, since it will be freed by virChrdevHashEntryFree
callback.

Preserve the error message before calling virStreamFree, since it
resets the error.

Reported by Sergey Fionov on libvir-list.
---
 src/conf/virchrdev.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/conf/virchrdev.c b/src/conf/virchrdev.c
index 025d4a8..879c27c 100644
--- a/src/conf/virchrdev.c
+++ b/src/conf/virchrdev.c
@@ -343,6 +343,8 @@ int virChrdevOpen(virChrdevsPtr devs,
     virStreamPtr savedStream;
     const char *path;
     int ret;
+    bool added = false;
+    virErrorPtr savedError;
 
     switch (source->type) {
     case VIR_DOMAIN_CHR_TYPE_PTY:
@@ -399,6 +401,7 @@ int virChrdevOpen(virChrdevsPtr devs,
 
     if (virHashAddEntry(devs->hash, path, st) < 0)
         goto error;
+    added = true;
 
     cbdata->devs = devs;
     if (!(cbdata->path = strdup(path))) {
@@ -433,8 +436,16 @@ int virChrdevOpen(virChrdevsPtr devs,
     return 0;
 
 error:
-    virStreamFree(st);
-    virHashRemoveEntry(devs->hash, path);
+    savedError = virSaveLastError();
+
+    if (added)
+        virHashRemoveEntry(devs->hash, path);
+    else
+        virStreamFree(st);
+
+    virSetError(savedError);
+    virFreeError(savedError);
+
     if (cbdata)
         VIR_FREE(cbdata->path);
     VIR_FREE(cbdata);
-- 
1.8.1.5