From 2b28a7bee4539d27f4ec3b0298f03bfd83d4f794 Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 12:53:33 +0300 Subject: fs, nfs: convert pnfs_layout_hdr.plh_refcount from atomic_t to refcount_t atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable pnfs_layout_hdr.plh_refcount is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova Signed-off-by: Anna Schumaker --- fs/nfs/pnfs.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'fs/nfs/pnfs.c') diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index 499bb710713e..4aab53baf664 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -251,7 +251,7 @@ EXPORT_SYMBOL_GPL(pnfs_unregister_layoutdriver); void pnfs_get_layout_hdr(struct pnfs_layout_hdr *lo) { - atomic_inc(&lo->plh_refcount); + refcount_inc(&lo->plh_refcount); } static struct pnfs_layout_hdr * @@ -296,7 +296,7 @@ pnfs_put_layout_hdr(struct pnfs_layout_hdr *lo) pnfs_layoutreturn_before_put_layout_hdr(lo); - if (atomic_dec_and_lock(&lo->plh_refcount, &inode->i_lock)) { + if (refcount_dec_and_lock(&lo->plh_refcount, &inode->i_lock)) { if (!list_empty(&lo->plh_segs)) WARN_ONCE(1, "NFS: BUG unfreed layout segments.\n"); pnfs_detach_layout_hdr(lo); @@ -395,14 +395,14 @@ pnfs_layout_set_fail_bit(struct pnfs_layout_hdr *lo, int fail_bit) { lo->plh_retry_timestamp = jiffies; if (!test_and_set_bit(fail_bit, &lo->plh_flags)) - atomic_inc(&lo->plh_refcount); + refcount_inc(&lo->plh_refcount); } static void pnfs_layout_clear_fail_bit(struct pnfs_layout_hdr *lo, int fail_bit) { if (test_and_clear_bit(fail_bit, &lo->plh_flags)) - atomic_dec(&lo->plh_refcount); + refcount_dec(&lo->plh_refcount); } static void @@ -472,7 +472,7 @@ pnfs_layout_remove_lseg(struct pnfs_layout_hdr *lo, WARN_ON(test_bit(NFS_LSEG_VALID, &lseg->pls_flags)); list_del_init(&lseg->pls_list); /* Matched by pnfs_get_layout_hdr in pnfs_layout_insert_lseg */ - atomic_dec(&lo->plh_refcount); + refcount_dec(&lo->plh_refcount); if (test_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags)) return; if (list_empty(&lo->plh_segs) && @@ -1451,7 +1451,7 @@ alloc_init_layout_hdr(struct inode *ino, lo = pnfs_alloc_layout_hdr(ino, gfp_flags); if (!lo) return NULL; - atomic_set(&lo->plh_refcount, 1); + refcount_set(&lo->plh_refcount, 1); INIT_LIST_HEAD(&lo->plh_layouts); INIT_LIST_HEAD(&lo->plh_segs); INIT_LIST_HEAD(&lo->plh_return_segs); -- cgit v1.2.3