Messages in this thread Patch in this message | | | From | "Aneesh Kumar K.V" <> | Subject | [PATCH -V18 04/13] vfs: Allow handle based open on symlinks | Date | Fri, 20 Aug 2010 07:21:28 +0530 |
| |
The patch update may_open to allow handle based open on symlinks. The file handle based API use file descritor returned from open_by_handle_at to do different file system operations. To find the link target name we need to get a file descriptor on symlinks.
We should be able to read the link target using file handle. The exact usecase is with respect to implementing READLINK operation on a userspace NFS server. The request contain the file handle and the response include target name.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> --- fs/namei.c | 24 ++++++++++++++++++++++-- include/asm-generic/fcntl.h | 1 + include/linux/fs.h | 1 + 3 files changed, 24 insertions(+), 2 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c index 1291dfc..2c79363 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1447,7 +1447,20 @@ int may_open(struct path *path, int acc_mode, int flag) switch (inode->i_mode & S_IFMT) { case S_IFLNK: - return -ELOOP; + /* + * Allow only if acc_mode contain + * open link request. + */ + if (!(acc_mode & MAY_OPEN_LINK)) + return -ELOOP; + /* + * Allow open on symlink only with + * open flag O_NOACCESS. We don't + * allow read/write on symlinks + */ + if (flag != O_NOACCESS) + return -ELOOP; + break; case S_IFDIR: if (acc_mode & MAY_WRITE) return -EISDIR; @@ -2038,8 +2051,15 @@ long do_handle_open(int mountdirfd, */ if (open_flag & __O_SYNC) open_flag |= O_DSYNC; + /* + * Handle based API allow open on a symlink + */ + if (S_ISLNK(path->dentry->d_inode->i_mode)) + acc_mode = MAY_OPEN_LINK; + else + acc_mode = MAY_OPEN; - acc_mode = MAY_OPEN | ACC_MODE(open_flag); + acc_mode |= ACC_MODE(open_flag); /* O_TRUNC implies we need access checks for write permissions */ if (open_flag & O_TRUNC) diff --git a/include/asm-generic/fcntl.h b/include/asm-generic/fcntl.h index a70b2d2..9d8f455 100644 --- a/include/asm-generic/fcntl.h +++ b/include/asm-generic/fcntl.h @@ -19,6 +19,7 @@ #define O_RDONLY 00000000 #define O_WRONLY 00000001 #define O_RDWR 00000002 +#define O_NOACCESS 00000003 /* No read/write access */ #ifndef O_CREAT #define O_CREAT 00000100 /* not fcntl */ #endif diff --git a/include/linux/fs.h b/include/linux/fs.h index e9471c7..3eb3571 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -55,6 +55,7 @@ struct inodes_stat_t { #define MAY_ACCESS 16 #define MAY_OPEN 32 #define MAY_CHDIR 64 +#define MAY_OPEN_LINK 128 /* * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond -- 1.7.0.4
| |