On Fri, 17 Jan 2014 14:07:06 +0400 Pavel Shilovsky <[email protected]> wrote:
> This patch adds 3 flags: > 1) O_DENYREAD that doesn't permit read access, > 2) O_DENYWRITE that doesn't permit write access, > 3) O_DENYDELETE that doesn't permit delete or rename. > > Network filesystems CIFS, SMB2.0, SMB3.0 and NFSv4 have such flags - > this change can benefit cifs and nfs modules as well as Samba and > NFS file servers that export the same directory for Windows clients, > or Wine applications that access the same files simultaneously. > > These flags are only take affect for opens on mounts with new sharelock > option. They are translated to flock's flags: > > !O_DENYREAD -> LOCK_READ | LOCK_MAND > !O_DENYWRITE -> LOCK_WRITE | LOCK_MAND > > and set through flock_lock_file on a file. If the file can't be locked > due conflicts with another open with O_DENY* flags, a new -ESHAREDENIED > error code is returned. > > Create codepath is slightly changed to prevent data races on newly > created files: when open with O_CREAT can return -ESHAREDENIED error > for successfully created files due to a sharelock set by another task. > > Temporary disable O_DENYDELETE support - will enable it in further > patches. > > Signed-off-by: Pavel Shilovsky <[email protected]> > --- > arch/alpha/include/uapi/asm/errno.h | 2 + > arch/alpha/include/uapi/asm/fcntl.h | 3 ++ > arch/mips/include/uapi/asm/errno.h | 2 + > arch/parisc/include/uapi/asm/errno.h | 2 + > arch/parisc/include/uapi/asm/fcntl.h | 3 ++ > arch/sparc/include/uapi/asm/errno.h | 2 + > arch/sparc/include/uapi/asm/fcntl.h | 3 ++ > fs/fcntl.c | 5 +- > fs/locks.c | 97 > +++++++++++++++++++++++++++++++--- > fs/namei.c | 53 ++++++++++++++++++- > fs/proc_namespace.c | 1 + > include/linux/fs.h | 8 +++ > include/uapi/asm-generic/errno.h | 2 + > include/uapi/asm-generic/fcntl.h | 11 ++++ > include/uapi/linux/fs.h | 1 + > 15 files changed, 185 insertions(+), 10 deletions(-) > You might consider breaking this patch into two. One patch that makes LOCK_MAND locks actually work and that adds MS_SHARELOCK, and one patch that hooks that up to open(). Given the locking involved with the i_mutex it would be best to present this as a series of small, incremental changes. > diff --git a/arch/alpha/include/uapi/asm/errno.h > b/arch/alpha/include/uapi/asm/errno.h > index 17f92aa..953a6d6 100644 > --- a/arch/alpha/include/uapi/asm/errno.h > +++ b/arch/alpha/include/uapi/asm/errno.h > @@ -124,4 +124,6 @@ > > #define EHWPOISON 139 /* Memory page has hardware error */ > > +#define ESHAREDENIED 140 /* File is locked with a sharelock */ > + > #endif > diff --git a/arch/alpha/include/uapi/asm/fcntl.h > b/arch/alpha/include/uapi/asm/fcntl.h > index 09f49a6..265344b 100644 > --- a/arch/alpha/include/uapi/asm/fcntl.h > +++ b/arch/alpha/include/uapi/asm/fcntl.h > @@ -33,6 +33,9 @@ > > #define O_PATH 040000000 > #define __O_TMPFILE 0100000000 > +#define O_DENYREAD 0200000000 /* Do not permit read access */ > +#define O_DENYWRITE 0400000000 /* Do not permit write access */ > +#define O_DENYDELETE 01000000000 /* Do not permit delete or rename */ > > #define F_GETLK 7 > #define F_SETLK 8 > diff --git a/arch/mips/include/uapi/asm/errno.h > b/arch/mips/include/uapi/asm/errno.h > index 02d645d..f1a4068 100644 > --- a/arch/mips/include/uapi/asm/errno.h > +++ b/arch/mips/include/uapi/asm/errno.h > @@ -123,6 +123,8 @@ > > #define EHWPOISON 168 /* Memory page has hardware error */ > > +#define ESHAREDENIED 169 /* File is locked with a sharelock */ > + > #define EDQUOT 1133 /* Quota exceeded */ > > > diff --git a/arch/parisc/include/uapi/asm/errno.h > b/arch/parisc/include/uapi/asm/errno.h > index f3a8aa5..654c232 100644 > --- a/arch/parisc/include/uapi/asm/errno.h > +++ b/arch/parisc/include/uapi/asm/errno.h > @@ -124,4 +124,6 @@ > > #define EHWPOISON 257 /* Memory page has hardware error */ > > +#define ESHAREDENIED 258 /* File is locked with a sharelock */ > + > #endif > diff --git a/arch/parisc/include/uapi/asm/fcntl.h > b/arch/parisc/include/uapi/asm/fcntl.h > index 34a46cb..5865964 100644 > --- a/arch/parisc/include/uapi/asm/fcntl.h > +++ b/arch/parisc/include/uapi/asm/fcntl.h > @@ -21,6 +21,9 @@ > > #define O_PATH 020000000 > #define __O_TMPFILE 040000000 > +#define O_DENYREAD 0200000000 /* Do not permit read access */ > +#define O_DENYWRITE 0400000000 /* Do not permit write access */ > +#define O_DENYDELETE 01000000000 /* Do not permit delete or rename */ > > #define F_GETLK64 8 > #define F_SETLK64 9 > diff --git a/arch/sparc/include/uapi/asm/errno.h > b/arch/sparc/include/uapi/asm/errno.h > index 20423e17..fe339b5 100644 > --- a/arch/sparc/include/uapi/asm/errno.h > +++ b/arch/sparc/include/uapi/asm/errno.h > @@ -114,4 +114,6 @@ > > #define EHWPOISON 135 /* Memory page has hardware error */ > > +#define ESHAREDENIED 136 /* File is locked with a sharelock */ > + > #endif > diff --git a/arch/sparc/include/uapi/asm/fcntl.h > b/arch/sparc/include/uapi/asm/fcntl.h > index 7e8ace5..ab68170 100644 > --- a/arch/sparc/include/uapi/asm/fcntl.h > +++ b/arch/sparc/include/uapi/asm/fcntl.h > @@ -36,6 +36,9 @@ > > #define O_PATH 0x1000000 > #define __O_TMPFILE 0x2000000 > +#define O_DENYREAD 0x4000000 /* Do not permit read access */ > +#define O_DENYWRITE 0x8000000 /* Do not permit write access */ > +#define O_DENYDELETE 0x10000000 /* Do not permit delete or rename */ > It'd probably be best to add O_DENYDELETE in a separate patch, rather than disabling it temporarily. > #define F_GETOWN 5 /* for sockets. */ > #define F_SETOWN 6 /* for sockets. */ > diff --git a/fs/fcntl.c b/fs/fcntl.c > index ef68665..3f85887 100644 > --- a/fs/fcntl.c > +++ b/fs/fcntl.c > @@ -729,14 +729,15 @@ static int __init fcntl_init(void) > * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY > * is defined as O_NONBLOCK on some platforms and not on others. > */ > - BUILD_BUG_ON(20 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32( > + BUILD_BUG_ON(23 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32( > O_RDONLY | O_WRONLY | O_RDWR | > O_CREAT | O_EXCL | O_NOCTTY | > O_TRUNC | O_APPEND | /* O_NONBLOCK | */ > __O_SYNC | O_DSYNC | FASYNC | > O_DIRECT | O_LARGEFILE | O_DIRECTORY | > O_NOFOLLOW | O_NOATIME | O_CLOEXEC | > - __FMODE_EXEC | O_PATH | __O_TMPFILE > + __FMODE_EXEC | O_PATH | __O_TMPFILE | > + O_DENYREAD | O_DENYWRITE | O_DENYDELETE > )); > > fasync_cache = kmem_cache_create("fasync_cache", > diff --git a/fs/locks.c b/fs/locks.c > index 92a0f0a..ffde4d4 100644 > --- a/fs/locks.c > +++ b/fs/locks.c > @@ -708,20 +708,73 @@ static int posix_locks_conflict(struct file_lock > *caller_fl, struct file_lock *s > return (locks_conflict(caller_fl, sys_fl)); > } > > -/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific > - * checking before calling the locks_conflict(). > +static unsigned int > +deny_flags_to_cmd(unsigned int flags) > +{ > + unsigned int cmd = LOCK_MAND; > + > + if (!(flags & O_DENYREAD)) > + cmd |= LOCK_READ; > + if (!(flags & O_DENYWRITE)) > + cmd |= LOCK_WRITE; > + > + return cmd; > +} > + > +/* > + * locks_mand_conflict - Determine if there's a share reservation conflict > + * @caller_fl: lock we're attempting to acquire > + * @sys_fl: lock already present on system that we're checking against > + * > + * Check to see if there's a share_reservation conflict. LOCK_READ/LOCK_WRITE > + * tell us whether the reservation allows other readers and writers. > + */ > +static int > +locks_mand_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl) > +{ > + unsigned char caller_type = caller_fl->fl_type; > + unsigned char sys_type = sys_fl->fl_type; > + fmode_t caller_fmode = caller_fl->fl_file->f_mode; > + fmode_t sys_fmode = sys_fl->fl_file->f_mode; > + > + /* they can only conflict if FS is mounted with MS_SHARELOCK */ > + if (!IS_SHARELOCK(caller_fl->fl_file->f_path.dentry->d_inode)) > + return 0; > + > + /* they can only conflict if they're both LOCK_MAND */ > + if (!(caller_type & LOCK_MAND) || !(sys_type & LOCK_MAND)) > + return 0; > + > + if (!(caller_type & LOCK_READ) && (sys_fmode & FMODE_READ)) > + return 1; > + if (!(caller_type & LOCK_WRITE) && (sys_fmode & FMODE_WRITE)) > + return 1; > + if (!(sys_type & LOCK_READ) && (caller_fmode & FMODE_READ)) > + return 1; > + if (!(sys_type & LOCK_WRITE) && (caller_fmode & FMODE_WRITE)) > + return 1; > + > + return 0; > +} > + > +/* > + * Determine if lock sys_fl blocks lock caller_fl. FLOCK specific checking > + * before calling the locks_conflict(). > */ > static int flock_locks_conflict(struct file_lock *caller_fl, struct > file_lock *sys_fl) > { > - /* FLOCK locks referring to the same filp do not conflict with > + if (!IS_FLOCK(sys_fl)) > + return 0; > + if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND)) > + return locks_mand_conflict(caller_fl, sys_fl); nit: Seems like the above could be optimized a little. You know that locks_mand_conflict is only relevant if both are LOCK_MAND, and one of the first things that locks_mand_conflict does is to check that both have that set. > + /* > + * FLOCK locks referring to the same filp do not conflict with > * each other. > */ > - if (!IS_FLOCK(sys_fl) || (caller_fl->fl_file == sys_fl->fl_file)) > - return (0); > - if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND)) > + if (caller_fl->fl_file == sys_fl->fl_file) > return 0; > > - return (locks_conflict(caller_fl, sys_fl)); > + return locks_conflict(caller_fl, sys_fl); > } > > void > @@ -888,6 +941,36 @@ out: > return error; > } > > +/* > + * Determine if a file is allowed to be opened with specified access and > share > + * modes. Lock the file and return 0 if checks passed, otherwise return > + * -ESHAREDENIED. > + */ > +int > +sharelock_lock_file(struct file *filp) > +{ > + struct file_lock *lock; > + int error = 0; > + > + if (!IS_SHARELOCK(filp->f_path.dentry->d_inode)) > + return error; > + > + /* Disable O_DENYDELETE support for now */ > + if (filp->f_flags & O_DENYDELETE) > + return -EINVAL; > + > + error = flock_make_lock(filp, &lock, deny_flags_to_cmd(filp->f_flags)); > + if (error) > + return error; > + > + error = flock_lock_file(filp, lock); > + if (error == -EAGAIN) > + error = -ESHAREDENIED; > + > + locks_free_lock(lock); > + return error; > +} > + > static int __posix_lock_file(struct inode *inode, struct file_lock *request, > struct file_lock *conflock) > { > struct file_lock *fl; > diff --git a/fs/namei.c b/fs/namei.c > index 3531dee..2b741a1 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -2725,9 +2725,14 @@ static int atomic_open(struct nameidata *nd, struct > dentry *dentry, > acc_mode = MAY_OPEN; > } > error = may_open(&file->f_path, acc_mode, open_flag); > - if (error) > + if (error) { > fput(file); > + goto out; > + } > > + error = sharelock_lock_file(file); > + if (error) > + fput(file); > out: > dput(dentry); > return error; > @@ -2919,6 +2924,40 @@ retry_lookup: > } > mutex_lock(&dir->d_inode->i_mutex); > error = lookup_open(nd, path, file, op, got_write, opened); > + > + /* > + * For sharelock mounts if a file was created but not opened, we need > + * to keep parent i_mutex until we finish the open to prevent races when > + * somebody opens newly created by us file and locks it with a sharelock > + * before we open it. > + */ > + if (IS_SHARELOCK(dir->d_inode) && error > 0 && *opened & FILE_CREATED) { > + /* Don't check for write permission, don't truncate */ > + open_flag &= ~O_TRUNC; > + will_truncate = false; > + acc_mode = MAY_OPEN; > + path_to_nameidata(path, nd); > + > + error = may_open(&nd->path, acc_mode, open_flag); > + if (error) { > + mutex_unlock(&dir->d_inode->i_mutex); > + goto out; > + } > + file->f_path.mnt = nd->path.mnt; > + error = finish_open(file, nd->path.dentry, NULL, opened); > + if (error) { > + mutex_unlock(&dir->d_inode->i_mutex); > + if (error == -EOPENSTALE) > + goto stale_open; > + goto out; > + } > + error = sharelock_lock_file(file); > + mutex_unlock(&dir->d_inode->i_mutex); > + if (error) > + goto exit_fput; > + goto opened; > + } > + > mutex_unlock(&dir->d_inode->i_mutex); > > if (error <= 0) { > @@ -3034,6 +3073,18 @@ finish_open_created: > goto stale_open; > goto out; > } > + > + if (IS_SHARELOCK(dir->d_inode)) { > + /* > + * Lock parent i_mutex to prevent races with sharelocks on > + * newly created files. > + */ > + mutex_lock(&dir->d_inode->i_mutex); > + error = sharelock_lock_file(file); > + mutex_unlock(&dir->d_inode->i_mutex); > + if (error) > + goto exit_fput; > + } > opened: > error = open_check_o_direct(file); > if (error) > diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c > index 439406e..dd374d4 100644 > --- a/fs/proc_namespace.c > +++ b/fs/proc_namespace.c > @@ -44,6 +44,7 @@ static int show_sb_opts(struct seq_file *m, struct > super_block *sb) > { MS_SYNCHRONOUS, ",sync" }, > { MS_DIRSYNC, ",dirsync" }, > { MS_MANDLOCK, ",mand" }, > + { MS_SHARELOCK, ",sharelock" }, > { 0, NULL } > }; > const struct proc_fs_info *fs_infop; > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 121f11f..aa061ca 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1029,6 +1029,7 @@ extern int vfs_setlease(struct file *, long, struct > file_lock **); > extern int lease_modify(struct file_lock **, int); > extern int lock_may_read(struct inode *, loff_t start, unsigned long count); > extern int lock_may_write(struct inode *, loff_t start, unsigned long count); > +extern int sharelock_lock_file(struct file *); > #else /* !CONFIG_FILE_LOCKING */ > static inline int fcntl_getlk(struct file *file, struct flock __user *user) > { > @@ -1169,6 +1170,12 @@ static inline int lock_may_write(struct inode *inode, > loff_t start, > { > return 1; > } > + > +static inline int sharelock_lock_file(struct file *filp) > +{ > + return 0; > +} > + > #endif /* !CONFIG_FILE_LOCKING */ > > > @@ -1675,6 +1682,7 @@ struct super_operations { > #define IS_PRIVATE(inode) ((inode)->i_flags & S_PRIVATE) > #define IS_IMA(inode) ((inode)->i_flags & S_IMA) > #define IS_AUTOMOUNT(inode) ((inode)->i_flags & S_AUTOMOUNT) > +#define IS_SHARELOCK(inode) __IS_FLG(inode, MS_SHARELOCK) > #define IS_NOSEC(inode) ((inode)->i_flags & S_NOSEC) > > /* > diff --git a/include/uapi/asm-generic/errno.h > b/include/uapi/asm-generic/errno.h > index 1e1ea6e..aff869c 100644 > --- a/include/uapi/asm-generic/errno.h > +++ b/include/uapi/asm-generic/errno.h > @@ -110,4 +110,6 @@ > > #define EHWPOISON 133 /* Memory page has hardware error */ > > +#define ESHAREDENIED 134 /* File is locked with a sharelock */ > + > #endif > diff --git a/include/uapi/asm-generic/fcntl.h > b/include/uapi/asm-generic/fcntl.h > index 95e46c8..9881cfe 100644 > --- a/include/uapi/asm-generic/fcntl.h > +++ b/include/uapi/asm-generic/fcntl.h > @@ -92,6 +92,17 @@ > #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY) > #define O_TMPFILE_MASK (__O_TMPFILE | O_DIRECTORY | O_CREAT) > > +#ifndef O_DENYREAD > +#define O_DENYREAD 040000000 /* Do not permit read access */ > +#endif > +/* FMODE_NONOTIFY 0100000000 */ > +#ifndef O_DENYWRITE > +#define O_DENYWRITE 0200000000 /* Do not permit write access */ > +#endif > +#ifndef O_DENYDELETE > +#define O_DENYDELETE 0400000000 /* Do not permit delete or rename */ > +#endif > + One thing to consider: We found with the addition of O_TMPFILE that the open() api is not particularly helpful when it comes to informing appications when a flag isn't supported: http://lwn.net/Articles/562294/ ...having a plan to cope with that here would be best. How can an application determine at runtime that O_DENY* actually *work*? It may be best to step back and consider a new syscall for this (open2() ?). > #ifndef O_NDELAY > #define O_NDELAY O_NONBLOCK > #endif > diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h > index 6c28b61..11f0ecf 100644 > --- a/include/uapi/linux/fs.h > +++ b/include/uapi/linux/fs.h > @@ -86,6 +86,7 @@ struct inodes_stat_t { > #define MS_KERNMOUNT (1<<22) /* this is a kern_mount call */ > #define MS_I_VERSION (1<<23) /* Update inode I_version field */ > #define MS_STRICTATIME (1<<24) /* Always perform atime updates */ > +#define MS_SHARELOCK (1<<25) /* Allow share locks on an FS */ > > /* These sb flags are internal to the kernel */ > #define MS_NOSEC (1<<28) -- Jeff Layton <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
