From 7e0e953bb0cf649f93277ac8fb67ecbb7f7b04a9 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 21 Feb 2015 22:16:11 -0500 Subject: procfs: fix race between symlink removals and traversals use_pde()/unuse_pde() in ->follow_link()/->put_link() resp. Cc: stable@vger.kernel.org Signed-off-by: Al Viro --- fs/proc/generic.c | 12 ------------ fs/proc/inode.c | 21 +++++++++++++++++++++ fs/proc/internal.h | 1 + 3 files changed, 22 insertions(+), 12 deletions(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index 3309f59d421b..be65b2082135 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -19,7 +19,6 @@ #include #include #include -#include #include #include #include @@ -223,17 +222,6 @@ void proc_free_inum(unsigned int inum) spin_unlock_irqrestore(&proc_inum_lock, flags); } -static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd) -{ - nd_set_link(nd, __PDE_DATA(dentry->d_inode)); - return NULL; -} - -static const struct inode_operations proc_link_inode_operations = { - .readlink = generic_readlink, - .follow_link = proc_follow_link, -}; - /* * Don't create negative dentries here, return -ENOENT by hand * instead. diff --git a/fs/proc/inode.c b/fs/proc/inode.c index 13a50a32652d..7697b6621cfd 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -23,6 +23,7 @@ #include #include #include +#include #include @@ -393,6 +394,26 @@ static const struct file_operations proc_reg_file_ops_no_compat = { }; #endif +static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd) +{ + struct proc_dir_entry *pde = PDE(dentry->d_inode); + if (unlikely(!use_pde(pde))) + return ERR_PTR(-EINVAL); + nd_set_link(nd, pde->data); + return pde; +} + +static void proc_put_link(struct dentry *dentry, struct nameidata *nd, void *p) +{ + unuse_pde(p); +} + +const struct inode_operations proc_link_inode_operations = { + .readlink = generic_readlink, + .follow_link = proc_follow_link, + .put_link = proc_put_link, +}; + struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de) { struct inode *inode = new_inode_pseudo(sb); diff --git a/fs/proc/internal.h b/fs/proc/internal.h index 6fcdba573e0f..c835b94c0cd3 100644 --- a/fs/proc/internal.h +++ b/fs/proc/internal.h @@ -200,6 +200,7 @@ struct pde_opener { int closing; struct completion *c; }; +extern const struct inode_operations proc_link_inode_operations; extern const struct inode_operations proc_pid_link_inode_operations; -- cgit v1.2.3