From: Alexey Dobriyan adobriyan@gmail.com
[ Upstream commit e06689bf57017ac022ccf0f2a5071f760821ce0f ]
Currently gluing PDE into global /proc tree is done under lock, but changing ->nlink is not. Additionally struct proc_dir_entry::nlink is not atomic so updates can be lost.
Link: http://lkml.kernel.org/r/20190925202436.GA17388@avx2 Signed-off-by: Alexey Dobriyan adobriyan@gmail.com Cc: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/proc/generic.c | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-)
diff --git a/fs/proc/generic.c b/fs/proc/generic.c index e39bac94dead0..7820fe524cb03 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -137,8 +137,12 @@ static int proc_getattr(const struct path *path, struct kstat *stat, { struct inode *inode = d_inode(path->dentry); struct proc_dir_entry *de = PDE(inode); - if (de && de->nlink) - set_nlink(inode, de->nlink); + if (de) { + nlink_t nlink = READ_ONCE(de->nlink); + if (nlink > 0) { + set_nlink(inode, nlink); + } + }
generic_fillattr(inode, stat); return 0; @@ -361,6 +365,7 @@ struct proc_dir_entry *proc_register(struct proc_dir_entry *dir, write_unlock(&proc_subdir_lock); goto out_free_inum; } + dir->nlink++; write_unlock(&proc_subdir_lock);
return dp; @@ -471,10 +476,7 @@ struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode, ent->data = data; ent->proc_fops = &proc_dir_operations; ent->proc_iops = &proc_dir_inode_operations; - parent->nlink++; ent = proc_register(parent, ent); - if (!ent) - parent->nlink--; } return ent; } @@ -504,10 +506,7 @@ struct proc_dir_entry *proc_create_mount_point(const char *name) ent->data = NULL; ent->proc_fops = NULL; ent->proc_iops = NULL; - parent->nlink++; ent = proc_register(parent, ent); - if (!ent) - parent->nlink--; } return ent; } @@ -665,8 +664,12 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent) len = strlen(fn);
de = pde_subdir_find(parent, fn, len); - if (de) + if (de) { rb_erase(&de->subdir_node, &parent->subdir); + if (S_ISDIR(de->mode)) { + parent->nlink--; + } + } write_unlock(&proc_subdir_lock); if (!de) { WARN(1, "name '%s'\n", name); @@ -675,9 +678,6 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
proc_entry_rundown(de);
- if (S_ISDIR(de->mode)) - parent->nlink--; - de->nlink = 0; WARN(pde_subdir_first(de), "%s: removing non-empty directory '%s/%s', leaking at least '%s'\n", __func__, de->parent->name, de->name, pde_subdir_first(de)->name); @@ -713,13 +713,12 @@ int remove_proc_subtree(const char *name, struct proc_dir_entry *parent) de = next; continue; } - write_unlock(&proc_subdir_lock); - - proc_entry_rundown(de); next = de->parent; if (S_ISDIR(de->mode)) next->nlink--; - de->nlink = 0; + write_unlock(&proc_subdir_lock); + + proc_entry_rundown(de); if (de == root) break; pde_put(de);