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fs: add vfs_parse_fs_param_source() helper

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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>
This commit is contained in:
Christian Brauner
2021-07-14 15:47:50 +02:00
committed by Linus Torvalds
parent 3b0462726e
commit d1d488d813
3 changed files with 43 additions and 27 deletions
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54
fs/fs_context.c
View File

@@ -79,6 +79,35 @@ static int vfs_parse_sb_flag(struct fs_context *fc, const char *key)
return -ENOPARAM;
}
/**
* 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
@@ -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");