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| author | Vitaly Chikunov <vt@altlinux.org> | 2022-02-16 21:18:21 +0300 |
|---|---|---|
| committer | Christian Schoenebeck <qemu_oss@crudebyte.com> | 2022-02-17 16:57:58 +0100 |
| commit | e64e27d5cb103b7764f1a05b6eda7e7fedd517c5 (patch) | |
| tree | 6f349f7536e1b2e9ee569f7363b9802e82fb8e20 /hw/9pfs/9p-synth.c | |
| parent | 494fbbd3ed46a14ef0924651c058b9b0dcb4a7b4 (diff) | |
| download | qemu-e64e27d5cb103b7764f1a05b6eda7e7fedd517c5.zip qemu-e64e27d5cb103b7764f1a05b6eda7e7fedd517c5.tar.gz qemu-e64e27d5cb103b7764f1a05b6eda7e7fedd517c5.tar.bz2 | |
9pfs: Fix segfault in do_readdir_many caused by struct dirent overread
`struct dirent' returned from readdir(3) could be shorter (or longer)
than `sizeof(struct dirent)', thus memcpy of sizeof length will overread
into unallocated page causing SIGSEGV. Example stack trace:
#0 0x00005555559ebeed v9fs_co_readdir_many (/usr/bin/qemu-system-x86_64 + 0x497eed)
#1 0x00005555559ec2e9 v9fs_readdir (/usr/bin/qemu-system-x86_64 + 0x4982e9)
#2 0x0000555555eb7983 coroutine_trampoline (/usr/bin/qemu-system-x86_64 + 0x963983)
#3 0x00007ffff73e0be0 n/a (n/a + 0x0)
While fixing this, provide a helper for any future `struct dirent' cloning.
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/841
Cc: qemu-stable@nongnu.org
Co-authored-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
Tested-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Acked-by: Greg Kurz <groug@kaod.org>
Tested-by: Vitaly Chikunov <vt@altlinux.org>
Message-Id: <20220216181821.3481527-1-vt@altlinux.org>
[C.S. - Fix typo in source comment. ]
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Diffstat (limited to 'hw/9pfs/9p-synth.c')
| -rw-r--r-- | hw/9pfs/9p-synth.c | 18 |
1 files changed, 15 insertions, 3 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; |