Merge remote-tracking branch 'remotes/cschoenebeck/tags/pull-9p-20220217' into staging

9pfs: fixes and cleanup

* Fifth patch fixes a 9pfs server crash that happened on some systems due
  to incorrect (system dependant) handling of struct dirent size.

* Tests: Second patch fixes a test error that happened on some systems due
  mkdir() being called twice for creating the test directory for the 9p
  'local' tests.

* Tests: Third patch fixes a memory leak.

* Tests: The remaining two patches are code cleanup.

# gpg: Signature made Thu 17 Feb 2022 16:19:25 GMT
# 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

* remotes/cschoenebeck/tags/pull-9p-20220217:
  9pfs: Fix segfault in do_readdir_many caused by struct dirent overread
  tests/9pfs: Use g_autofree and g_autoptr where possible
  tests/9pfs: Fix leak of local_test_path
  tests/9pfs: fix mkdir() being called twice
  tests/9pfs: use g_autofree where possible

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

3 files changed, 21 insertions, 5 deletions

diff --git a/hw/9pfs/9p-synth.c b/hw/9pfs/9p-synth.c
index b38088e..7a7cd5c 100644
--- a/hw/9pfs/9p-synth.c
+++ b/hw/9pfs/9p-synth.c
@@ -182,7 +182,12 @@ static int synth_opendir(FsContext *ctx,
     V9fsSynthOpenState *synth_open;
     V9fsSynthNode *node = *(V9fsSynthNode **)fs_path->data;
 
-    synth_open = g_malloc(sizeof(*synth_open));
+    /*
+     * V9fsSynthOpenState contains 'struct dirent' which have OS-specific
+     * properties, thus it's zero cleared on allocation here and below
+     * in synth_open.
+     */
+    synth_open = g_new0(V9fsSynthOpenState, 1);
     synth_open->node = node;
     node->open_count++;
     fs->private = synth_open;
@@ -220,7 +225,14 @@ static void synth_rewinddir(FsContext *ctx, V9fsFidOpenState *fs)
 static void synth_direntry(V9fsSynthNode *node,
                                 struct dirent *entry, off_t off)
 {
-    strcpy(entry->d_name, node->name);
+    size_t sz = strlen(node->name) + 1;
+    /*
+     * 'entry' is always inside of V9fsSynthOpenState which have NAME_MAX
+     * back padding. Ensure we do not overflow it.
+     */
+    g_assert(sizeof(struct dirent) + NAME_MAX >=
+             offsetof(struct dirent, d_name) + sz);
+    memcpy(entry->d_name, node->name, sz);
     entry->d_ino = node->attr->inode;
     entry->d_off = off + 1;
 }
@@ -266,7 +278,7 @@ static int synth_open(FsContext *ctx, V9fsPath *fs_path,
     V9fsSynthOpenState *synth_open;
     V9fsSynthNode *node = *(V9fsSynthNode **)fs_path->data;
 
-    synth_open = g_malloc(sizeof(*synth_open));
+    synth_open = g_new0(V9fsSynthOpenState, 1);
     synth_open->node = node;
     node->open_count++;
     fs->private = synth_open;
diff --git a/hw/9pfs/9p-synth.h b/hw/9pfs/9p-synth.h
index 036d7e4..eeb246f 100644
--- a/hw/9pfs/9p-synth.h
+++ b/hw/9pfs/9p-synth.h
@@ -41,6 +41,11 @@ typedef struct V9fsSynthOpenState {
     off_t offset;
     V9fsSynthNode *node;
     struct dirent dent;
+    /*
+     * Ensure there is enough space for 'dent' above, some systems have a
+     * d_name size of just 1, which would cause a buffer overrun.
+     */
+    char dent_trailing_space[NAME_MAX];
 } V9fsSynthOpenState;
 
 int qemu_v9fs_synth_mkdir(V9fsSynthNode *parent, int mode,
diff --git a/hw/9pfs/codir.c b/hw/9pfs/codir.c
index 032cce0..c0873bd 100644
--- a/hw/9pfs/codir.c
+++ b/hw/9pfs/codir.c
@@ -143,8 +143,7 @@ static int do_readdir_many(V9fsPDU *pdu, V9fsFidState *fidp,
         } else {
             e = e->next = g_malloc0(sizeof(V9fsDirEnt));
         }
-        e->dent = g_malloc0(sizeof(struct dirent));
-        memcpy(e->dent, dent, sizeof(struct dirent));
+        e->dent = qemu_dirent_dup(dent);
 
         /* perform a full stat() for directory entry if requested by caller */
         if (dostat) {