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authorChristian Brauner <christian.brauner@ubuntu.com>2021-07-14 15:47:50 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2021-07-14 09:19:06 -0700
commitd1d488d813703618f0dd93f0e4c4a05928114aa8 (patch)
treeb1115033156bb1945244b3000489d84a4b5a68ee
parent3b0462726e7ef281c35a7a4ae33e93ee2bc9975b (diff)
fs: add vfs_parse_fs_param_source() helper
Add a simple helper that filesystems can use in their parameter parser to parse the "source" parameter. A few places open-coded this function and that already caused a bug in the cgroup v1 parser that we fixed. Let's make it harder to get this wrong by introducing a helper which performs all necessary checks. Link: https://syzkaller.appspot.com/bug?id=6312526aba5beae046fdae8f00399f87aab48b12 Cc: Christoph Hellwig <hch@lst.de> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/fs_context.c54
-rw-r--r--include/linux/fs_context.h2
-rw-r--r--kernel/cgroup/cgroup-v1.c14
3 files changed, 43 insertions, 27 deletions
diff --git a/fs/fs_context.c b/fs/fs_context.c
index 2834d1afa6e8..de1985eae535 100644
--- a/fs/fs_context.c
+++ b/fs/fs_context.c
@@ -80,6 +80,35 @@ static int vfs_parse_sb_flag(struct fs_context *fc, const char *key)
}
/**
+ * vfs_parse_fs_param_source - Handle setting "source" via parameter
+ * @fc: The filesystem context to modify
+ * @param: The parameter
+ *
+ * This is a simple helper for filesystems to verify that the "source" they
+ * accept is sane.
+ *
+ * Returns 0 on success, -ENOPARAM if this is not "source" parameter, and
+ * -EINVAL otherwise. In the event of failure, supplementary error information
+ * is logged.
+ */
+int vfs_parse_fs_param_source(struct fs_context *fc, struct fs_parameter *param)
+{
+ if (strcmp(param->key, "source") != 0)
+ return -ENOPARAM;
+
+ if (param->type != fs_value_is_string)
+ return invalf(fc, "Non-string source");
+
+ if (fc->source)
+ return invalf(fc, "Multiple sources");
+
+ fc->source = param->string;
+ param->string = NULL;
+ return 0;
+}
+EXPORT_SYMBOL(vfs_parse_fs_param_source);
+
+/**
* vfs_parse_fs_param - Add a single parameter to a superblock config
* @fc: The filesystem context to modify
* @param: The parameter
@@ -122,15 +151,9 @@ int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param)
/* If the filesystem doesn't take any arguments, give it the
* default handling of source.
*/
- if (strcmp(param->key, "source") == 0) {
- if (param->type != fs_value_is_string)
- return invalf(fc, "VFS: Non-string source");
- if (fc->source)
- return invalf(fc, "VFS: Multiple sources");
- fc->source = param->string;
- param->string = NULL;
- return 0;
- }
+ ret = vfs_parse_fs_param_source(fc, param);
+ if (ret != -ENOPARAM)
+ return ret;
return invalf(fc, "%s: Unknown parameter '%s'",
fc->fs_type->name, param->key);
@@ -504,16 +527,11 @@ static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)
struct legacy_fs_context *ctx = fc->fs_private;
unsigned int size = ctx->data_size;
size_t len = 0;
+ int ret;
- if (strcmp(param->key, "source") == 0) {
- if (param->type != fs_value_is_string)
- return invalf(fc, "VFS: Legacy: Non-string source");
- if (fc->source)
- return invalf(fc, "VFS: Legacy: Multiple sources");
- fc->source = param->string;
- param->string = NULL;
- return 0;
- }
+ ret = vfs_parse_fs_param_source(fc, param);
+ if (ret != -ENOPARAM)
+ return ret;
if (ctx->param_type == LEGACY_FS_MONOLITHIC_PARAMS)
return invalf(fc, "VFS: Legacy: Can't mix monolithic and individual options");
diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h
index 37e1e8f7f08d..e2bc16300c82 100644
--- a/include/linux/fs_context.h
+++ b/include/linux/fs_context.h
@@ -139,6 +139,8 @@ extern int vfs_parse_fs_string(struct fs_context *fc, const char *key,
extern int generic_parse_monolithic(struct fs_context *fc, void *data);
extern int vfs_get_tree(struct fs_context *fc);
extern void put_fs_context(struct fs_context *fc);
+extern int vfs_parse_fs_param_source(struct fs_context *fc,
+ struct fs_parameter *param);
/*
* sget() wrappers to be called from the ->get_tree() op.
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 527917c0b30b..8d6bf56ed77a 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -911,15 +911,11 @@ int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param)
opt = fs_parse(fc, cgroup1_fs_parameters, param, &result);
if (opt == -ENOPARAM) {
- if (strcmp(param->key, "source") == 0) {
- if (param->type != fs_value_is_string)
- return invalf(fc, "Non-string source");
- if (fc->source)
- return invalf(fc, "Multiple sources not supported");
- fc->source = param->string;
- param->string = NULL;
- return 0;
- }
+ int ret;
+
+ ret = vfs_parse_fs_param_source(fc, param);
+ if (ret != -ENOPARAM)
+ return ret;
for_each_subsys(ss, i) {
if (strcmp(param->key, ss->legacy_name))
continue;