From d83c49f3e36cecd2e8823b6c48ffba083b8a5704 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 30 Apr 2010 17:17:09 -0400 Subject: Fix the regression created by "set S_DEAD on unlink()..." commit 1) i_flags simply doesn't work for mount/unlink race prevention; we may have many links to file and rm on one of those obviously shouldn't prevent bind on top of another later on. To fix it right way we need to mark _dentry_ as unsuitable for mounting upon; new flag (DCACHE_CANT_MOUNT) is protected by d_flags and i_mutex on the inode in question. Set it (with dont_mount(dentry)) in unlink/rmdir/etc., check (with cant_mount(dentry)) in places in namespace.c that used to check for S_DEAD. Setting S_DEAD is still needed in places where we used to set it (for directories getting killed), since we rely on it for readdir/rmdir race prevention. 2) rename()/mount() protection has another bogosity - we unhash the target before we'd checked that it's not a mountpoint. Fixed. 3) ancient bogosity in pivot_root() - we locked i_mutex on the right directory, but checked S_DEAD on the different (and wrong) one. Noticed and fixed. Signed-off-by: Al Viro --- include/linux/dcache.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'include/linux/dcache.h') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 30b93b2a01a4..eebb617c17d8 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -186,6 +186,8 @@ d_iput: no no no yes #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 /* Parent inode is watched by some fsnotify listener */ +#define DCACHE_CANT_MOUNT 0x0100 + extern spinlock_t dcache_lock; extern seqlock_t rename_lock; @@ -358,6 +360,18 @@ static inline int d_unlinked(struct dentry *dentry) return d_unhashed(dentry) && !IS_ROOT(dentry); } +static inline int cant_mount(struct dentry *dentry) +{ + return (dentry->d_flags & DCACHE_CANT_MOUNT); +} + +static inline void dont_mount(struct dentry *dentry) +{ + spin_lock(&dentry->d_lock); + dentry->d_flags |= DCACHE_CANT_MOUNT; + spin_unlock(&dentry->d_lock); +} + static inline struct dentry *dget_parent(struct dentry *dentry) { struct dentry *ret; -- cgit v1.2.2 From c103135c14e03fc9a9e5f0adc01df9ad272cf2a1 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 6 Jun 2010 22:31:14 -0400 Subject: new helper: __dentry_path() builds path relative to fs root, called under dcache_lock, doesn't append any nonsense to unlinked ones. Signed-off-by: Al Viro --- include/linux/dcache.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/dcache.h') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index eebb617c17d8..d23be0386e2d 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -315,6 +315,7 @@ extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...); extern char *__d_path(const struct path *path, struct path *root, char *, int); extern char *d_path(const struct path *, char *, int); +extern char *__dentry_path(struct dentry *, char *, int); extern char *dentry_path(struct dentry *, char *, int); /* Allocation counts.. */ -- cgit v1.2.2 From 8df9d1a4142311c084ffeeacb67cd34d190eff74 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Tue, 10 Aug 2010 11:41:41 +0200 Subject: vfs: show unreachable paths in getcwd and proc Prepend "(unreachable)" to path strings if the path is not reachable from the current root. Two places updated are - the return string from getcwd() - and symlinks under /proc/$PID. Other uses of d_path() are left unchanged (we know that some old software crashes if /proc/mounts is changed). Signed-off-by: Miklos Szeredi Signed-off-by: Al Viro --- include/linux/dcache.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/dcache.h') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index d23be0386e2d..6a4aea30aa09 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -315,6 +315,7 @@ extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...); extern char *__d_path(const struct path *path, struct path *root, char *, int); extern char *d_path(const struct path *, char *, int); +extern char *d_path_with_unreachable(const struct path *, char *, int); extern char *__dentry_path(struct dentry *, char *, int); extern char *dentry_path(struct dentry *, char *, int); -- cgit v1.2.2