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Kernel+Base: Introduce MS_NOREGULAR mount flag

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This flag doesn't conform to any POSIX standard nor is found in any OS
out there. The idea behind this mount flag is to ensure that only
non-regular files will be placed in a filesystem, which includes device
nodes, symbolic links, directories, FIFOs and sockets. Currently, the
only valid case for using this mount flag is for TmpFS instances, where
we want to mount a TmpFS but disallow any kind of regular file and only
allow other types of files on the filesystem.
This commit is contained in:
Liav A 2022-10-21 19:29:50 +03:00 • committed by Linus Groh
parent 97f8927da6
commit 07387ec19a
3 changed files with 7 additions and 0 deletions
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5
Kernel/FileSystem/VirtualFileSystem.cpp
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@ -263,6 +263,9 @@ ErrorOr<NonnullLockRefPtr<OpenFileDescription>> VirtualFileSystem::open(Credenti
auto& inode = custody.inode();
auto metadata = inode.metadata();
if (metadata.is_regular_file() && (custody.mount_flags() & MS_NOREGULAR))
return EACCES;
if ((options & O_DIRECTORY) && !metadata.is_directory())
return ENOTDIR;
@ -370,6 +373,8 @@ ErrorOr<NonnullLockRefPtr<OpenFileDescription>> VirtualFileSystem::create(Creden
return EACCES;
if (parent_custody.is_readonly())
return EROFS;
if (is_regular_file(mode) && (parent_custody.mount_flags() & MS_NOREGULAR))
return EACCES;
dbgln_if(VFS_DEBUG, "VirtualFileSystem::create: '{}' in {}", basename, parent_inode.identifier());
auto uid = owner.has_value() ? owner.value().uid : credentials.euid();