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actiondfs: use mount credentials for Landlock-safe backing opens #44

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actiondfs: use mount credentials for Landlock-safe backing opens #44

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25 changes: 21 additions & 4 deletions kernel/actiondfs/actiondfs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,7 @@ struct actiondfs_node {
struct actiondfs_sb_info {
struct path cas_path;
struct path stage_path;
const struct cred *creator_cred;
u8 root_hash[ACTIONDFS_HASH_LEN];
};

Expand Down Expand Up @@ -1116,8 +1117,11 @@ static struct file *actiondfs_open_directory_blob(struct actiondfs_sb_info *sbi,
if (IS_ERR(real_path.dentry)) {
file = ERR_CAST(real_path.dentry);
} else {
const struct cred *old_cred = override_creds(sbi->creator_cred);

file = kernel_file_open(&real_path, O_RDONLY | O_NONBLOCK,
current_cred());
revert_creds(old_cred);
dput(real_path.dentry);
}
if (!IS_ERR(file))
Expand Down Expand Up @@ -1167,8 +1171,13 @@ static struct file *actiondfs_open_backing_cas_blob(struct actiondfs_sb_info *sb
}

open_start = actiondfs_stat_time_start();
file = backing_file_open(user_path, O_RDONLY, &real_path,
current_cred());
{
const struct cred *old_cred = override_creds(sbi->creator_cred);

file = backing_file_open(user_path, O_RDONLY, &real_path,
current_cred());
revert_creds(old_cred);
}
actiondfs_stat_add_elapsed(ACTIONDFS_STAT_BLOB_OPEN_BACKING_FILE_NS,
open_start);
dput(real_path.dentry);
Expand Down Expand Up @@ -1226,8 +1235,13 @@ static struct file *actiondfs_open_staged_backing(struct actiondfs_sb_info *sbi,
}

phase_start = actiondfs_stat_time_start();
file = backing_file_open(file_user_path(actiondfs_file), flags,
&real_path, current_cred());
{
const struct cred *old_cred = override_creds(sbi->creator_cred);

file = backing_file_open(file_user_path(actiondfs_file), flags,
&real_path, current_cred());
revert_creds(old_cred);
}
actiondfs_stat_add_elapsed(ACTIONDFS_STAT_STAGE_BACKING_OPEN_FILE_NS,
phase_start);
out:
Expand Down Expand Up @@ -3403,6 +3417,8 @@ static void actiondfs_put_super(struct super_block *sb)
path_put(&sbi->cas_path);
if (sbi->stage_path.dentry)
path_put(&sbi->stage_path);
if (sbi->creator_cred)
put_cred(sbi->creator_cred);
kfree(sbi);
sb->s_fs_info = NULL;
}
Expand All @@ -3427,6 +3443,7 @@ static int actiondfs_fill_super(struct super_block *sb, struct fs_context *fc)
sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
if (!sbi)
return -ENOMEM;
sbi->creator_cred = get_current_cred();

sb->s_fs_info = sbi;
sb->s_magic = ACTIONDFS_MAGIC;
Expand Down