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author | Christian Brauner <christian.brauner@ubuntu.com> | 2021-07-14 15:47:50 +0200 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-07-14 18:19:06 +0200 |
commit | d1d488d813703618f0dd93f0e4c4a05928114aa8 (patch) | |
tree | b1115033156bb1945244b3000489d84a4b5a68ee | |
parent | cgroup: verify that source is a string (diff) | |
download | linux-d1d488d813703618f0dd93f0e4c4a05928114aa8.tar.xz linux-d1d488d813703618f0dd93f0e4c4a05928114aa8.zip |
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.c | 54 | ||||
-rw-r--r-- | include/linux/fs_context.h | 2 | ||||
-rw-r--r-- | kernel/cgroup/cgroup-v1.c | 14 |
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; |