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fuse: convert fuse_req.count from atomic_t to refcount_t

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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 <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Elena Reshetova 2017-03-03 11:04:04 +02:00 committed by Miklos Szeredi
parent 4e8c2eb543
commit ec99f6d31f
2 changed files with 5 additions and 6 deletions
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9
fs/fuse/dev.c
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@ -45,7 +45,7 @@ static void fuse_request_init(struct fuse_req *req, struct page **pages,
INIT_LIST_HEAD(&req->list);
INIT_LIST_HEAD(&req->intr_entry);
init_waitqueue_head(&req->waitq);
atomic_set(&req->count, 1);
refcount_set(&req->count, 1);
req->pages = pages;
req->page_descs = page_descs;
req->max_pages = npages;
@ -102,14 +102,13 @@ void fuse_request_free(struct fuse_req *req)
void __fuse_get_request(struct fuse_req *req)
{
atomic_inc(&req->count);
refcount_inc(&req->count);
}
/* Must be called with > 1 refcount */
static void __fuse_put_request(struct fuse_req *req)
{
BUG_ON(atomic_read(&req->count) < 2);
atomic_dec(&req->count);
refcount_dec(&req->count);
}
static void fuse_req_init_context(struct fuse_req *req)
@ -264,7 +263,7 @@ struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
{
if (atomic_dec_and_test(&req->count)) {
if (refcount_dec_and_test(&req->count)) {
if (test_bit(FR_BACKGROUND, &req->flags)) {
/*
* We get here in the unlikely case that a background

2
fs/fuse/fuse_i.h
View file

@ -307,7 +307,7 @@ struct fuse_req {
struct list_head intr_entry;
/** refcount */
atomic_t count;
refcount_t count;
/** Unique ID for the interrupt request */
u64 intr_unique;