refcount_t type and corresponding API should be used instead of atomic_t when the variable is used as a reference counter. This allows to avoid accidental refcounter overflows that might lead to use-after-free situations.
Signed-off-by: Elena Reshetova <[email protected]> Signed-off-by: Hans Liljestrand <[email protected]> Signed-off-by: Kees Cook <[email protected]> Signed-off-by: David Windsor <[email protected]> --- fs/proc/generic.c | 4 ++-- fs/proc/internal.h | 5 +++-- fs/proc/root.c | 2 +- 3 files changed, 6 insertions(+), 5 deletions(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index ee27feb..0850766 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -388,7 +388,7 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent, ent->mode = mode; ent->nlink = nlink; ent->subdir = RB_ROOT; - atomic_set(&ent->count, 1); + refcount_set(&ent->count, 1); spin_lock_init(&ent->pde_unload_lock); INIT_LIST_HEAD(&ent->pde_openers); proc_set_user(ent, (*parent)->uid, (*parent)->gid); @@ -540,7 +540,7 @@ static void free_proc_entry(struct proc_dir_entry *de) void pde_put(struct proc_dir_entry *pde) { - if (atomic_dec_and_test(&pde->count)) + if (refcount_dec_and_test(&pde->count)) free_proc_entry(pde); } diff --git a/fs/proc/internal.h b/fs/proc/internal.h index e93cdc6..7b5fa12 100644 --- a/fs/proc/internal.h +++ b/fs/proc/internal.h @@ -13,6 +13,7 @@ #include <linux/proc_ns.h> #include <linux/spinlock.h> #include <linux/atomic.h> +#include <linux/refcount.h> #include <linux/binfmts.h> struct ctl_table_header; @@ -41,7 +42,7 @@ struct proc_dir_entry { struct rb_root subdir; struct rb_node subdir_node; void *data; - atomic_t count; /* use count */ + refcount_t count; /* use count */ atomic_t in_use; /* number of callers into module in progress; */ /* negative -> it's going away RSN */ struct completion *pde_unload_completion; @@ -175,7 +176,7 @@ extern int proc_readdir_de(struct proc_dir_entry *, struct file *, struct dir_co static inline struct proc_dir_entry *pde_get(struct proc_dir_entry *pde) { - atomic_inc(&pde->count); + refcount_inc(&pde->count); return pde; } extern void pde_put(struct proc_dir_entry *); diff --git a/fs/proc/root.c b/fs/proc/root.c index fb1955c..882bcb5 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -204,7 +204,7 @@ struct proc_dir_entry proc_root = { .namelen = 5, .mode = S_IFDIR | S_IRUGO | S_IXUGO, .nlink = 2, - .count = ATOMIC_INIT(1), + .count = REFCOUNT_INIT(1), .proc_iops = &proc_root_inode_operations, .proc_fops = &proc_root_operations, .parent = &proc_root, -- 2.7.4
