diff options
| -rw-r--r-- | fs/pidfs.c | 78 | ||||
| -rw-r--r-- | include/linux/pidfs.h | 2 | ||||
| -rw-r--r-- | kernel/pid.c | 14 |
3 files changed, 86 insertions, 8 deletions
diff --git a/fs/pidfs.c b/fs/pidfs.c index 618abb1fa1b8..abfe96be9ffe 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -23,6 +23,79 @@ #include "internal.h" #include "mount.h" +static DEFINE_IDR(pidfs_ino_idr); + +static u32 pidfs_ino_upper_32_bits = 0; + +#if BITS_PER_LONG == 32 +/* + * On 32 bit systems the lower 32 bits are the inode number and + * the higher 32 bits are the generation number. The starting + * value for the inode number and the generation number is one. + */ +static u32 pidfs_ino_lower_32_bits = 1; + +static inline unsigned long pidfs_ino(u64 ino) +{ + return lower_32_bits(ino); +} + +/* On 32 bit the generation number are the upper 32 bits. */ +static inline u32 pidfs_gen(u64 ino) +{ + return upper_32_bits(ino); +} + +#else + +static u32 pidfs_ino_lower_32_bits = 0; + +/* On 64 bit simply return ino. */ +static inline unsigned long pidfs_ino(u64 ino) +{ + return ino; +} + +/* On 64 bit the generation number is 1. */ +static inline u32 pidfs_gen(u64 ino) +{ + return 1; +} +#endif + +/* + * Construct an inode number for struct pid in a way that we can use the + * lower 32bit to lookup struct pid independent of any pid numbers that + * could be leaked into userspace (e.g., via file handle encoding). + */ +int pidfs_add_pid(struct pid *pid) +{ + u32 upper; + int lower; + + /* + * Inode numbering for pidfs start at 2. This avoids collisions + * with the root inode which is 1 for pseudo filesystems. + */ + lower = idr_alloc_cyclic(&pidfs_ino_idr, pid, 2, 0, GFP_ATOMIC); + if (lower >= 0 && lower < pidfs_ino_lower_32_bits) + pidfs_ino_upper_32_bits++; + upper = pidfs_ino_upper_32_bits; + pidfs_ino_lower_32_bits = lower; + if (lower < 0) + return lower; + + pid->ino = ((u64)upper << 32) | lower; + pid->stashed = NULL; + return 0; +} + +/* The idr number to remove is the lower 32 bits of the inode. */ +void pidfs_remove_pid(struct pid *pid) +{ + idr_remove(&pidfs_ino_idr, lower_32_bits(pid->ino)); +} + #ifdef CONFIG_PROC_FS /** * pidfd_show_fdinfo - print information about a pidfd @@ -346,7 +419,7 @@ static inline void pidfs_free_inum(unsigned long ino) #else static inline int pidfs_inum(struct pid *pid, unsigned long *ino) { - *ino = pid->ino; + *ino = pidfs_ino(pid->ino); return 0; } #define pidfs_free_inum(ino) ((void)(ino)) @@ -429,11 +502,14 @@ static const struct dentry_operations pidfs_dentry_operations = { static int pidfs_init_inode(struct inode *inode, void *data) { + const struct pid *pid = data; + inode->i_private = data; inode->i_flags |= S_PRIVATE; inode->i_mode |= S_IRWXU; inode->i_op = &pidfs_inode_operations; inode->i_fop = &pidfs_file_operations; + inode->i_generation = pidfs_gen(pid->ino); /* * Inode numbering for pidfs start at RESERVED_PIDS + 1. This * avoids collisions with the root inode which is 1 for pseudo diff --git a/include/linux/pidfs.h b/include/linux/pidfs.h index 75bdf9807802..2958652bb108 100644 --- a/include/linux/pidfs.h +++ b/include/linux/pidfs.h @@ -4,5 +4,7 @@ struct file *pidfs_alloc_file(struct pid *pid, unsigned int flags); void __init pidfs_init(void); +int pidfs_add_pid(struct pid *pid); +void pidfs_remove_pid(struct pid *pid); #endif /* _LINUX_PID_FS_H */ diff --git a/kernel/pid.c b/kernel/pid.c index 115448e89c3e..58567d6904b2 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -64,11 +64,6 @@ int pid_max = PID_MAX_DEFAULT; int pid_max_min = RESERVED_PIDS + 1; int pid_max_max = PID_MAX_LIMIT; -/* - * Pseudo filesystems start inode numbering after one. We use Reserved - * PIDs as a natural offset. - */ -static u64 pidfs_ino = RESERVED_PIDS; /* * PID-map pages start out as NULL, they get allocated upon @@ -158,6 +153,7 @@ void free_pid(struct pid *pid) idr_remove(&ns->idr, upid->nr); } + pidfs_remove_pid(pid); spin_unlock_irqrestore(&pidmap_lock, flags); call_rcu(&pid->rcu, delayed_put_pid); @@ -273,22 +269,26 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid, INIT_HLIST_HEAD(&pid->inodes); upid = pid->numbers + ns->level; + idr_preload(GFP_KERNEL); spin_lock_irq(&pidmap_lock); if (!(ns->pid_allocated & PIDNS_ADDING)) goto out_unlock; - pid->stashed = NULL; - pid->ino = ++pidfs_ino; + retval = pidfs_add_pid(pid); + if (retval) + goto out_unlock; for ( ; upid >= pid->numbers; --upid) { /* Make the PID visible to find_pid_ns. */ idr_replace(&upid->ns->idr, pid, upid->nr); upid->ns->pid_allocated++; } spin_unlock_irq(&pidmap_lock); + idr_preload_end(); return pid; out_unlock: spin_unlock_irq(&pidmap_lock); + idr_preload_end(); put_pid_ns(ns); out_free: |