From: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Date: Wed, 4 Jun 2025 22:41:06 +0000 (-0700)
Subject: ceph: fix overflowed value issue in ceph_submit_write()
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=9233d2c1fd2d072e9d85e14c2adb804df28c8c23;p=ceph-client.git

ceph: fix overflowed value issue in ceph_submit_write()

The Coverity Scan service has detected overflowed value
issue in ceph_submit_write() [1]. The CID 1646339 defect
contains explanation: "The overflowed value due to
arithmetic on constants is too small or unexpectedly
negative, causing incorrect computations.
In ceph_submit_write: Integer overflow occurs in
arithmetic on constant operands (CWE-190)".

This patch adds a check ceph_wbc->locked_pages on
equality to zero and it exits function if it has
zero value. Also, it introduces a processed_pages
variable with the goal of assigning the number of
processed pages and checking this number on
equality to zero. The check of processed_pages
variable on equality to zero should protect from
overflowed value of index that selects page in
ceph_wbc->pages[index] array.

[1] https://scan5.scan.coverity.com/#/project-view/64304/10063?selectedIssue=1646339

Signed-off-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
---

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 5a5751156f8b..a4ffa2b63184 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -1418,6 +1418,7 @@ int ceph_submit_write(struct address_space *mapping,
 	bool caching = ceph_is_cache_enabled(inode);
 	u64 offset;
 	u64 len;
+	unsigned processed_pages;
 	unsigned i;
 
 new_request:
@@ -1445,6 +1446,9 @@ new_request:
 		BUG_ON(IS_ERR(req));
 	}
 
+	if (ceph_wbc->locked_pages == 0)
+		return -EINVAL;
+
 	page = ceph_wbc->pages[ceph_wbc->locked_pages - 1];
 	BUG_ON(len < ceph_fscrypt_page_offset(page) + thp_size(page) - offset);
 
@@ -1481,6 +1485,7 @@ new_request:
 	len = 0;
 	ceph_wbc->data_pages = ceph_wbc->pages;
 	ceph_wbc->op_idx = 0;
+	processed_pages = 0;
 	for (i = 0; i < ceph_wbc->locked_pages; i++) {
 		u64 cur_offset;
 
@@ -1524,19 +1529,22 @@ new_request:
 			ceph_set_page_fscache(page);
 
 		len += thp_size(page);
+		processed_pages++;
 	}
 
 	ceph_fscache_write_to_cache(inode, offset, len, caching);
 
 	if (ceph_wbc->size_stable) {
 		len = min(len, ceph_wbc->i_size - offset);
-	} else if (i == ceph_wbc->locked_pages) {
+	} else if (processed_pages > 0 &&
+		   processed_pages == ceph_wbc->locked_pages) {
 		/* writepages_finish() clears writeback pages
 		 * according to the data length, so make sure
 		 * data length covers all locked pages */
 		u64 min_len = len + 1 - thp_size(page);
+		unsigned index = processed_pages - 1;
 		len = get_writepages_data_length(inode,
-						 ceph_wbc->pages[i - 1],
+						 ceph_wbc->pages[index],
 						 offset);
 		len = max(len, min_len);
 	}
@@ -1561,17 +1569,17 @@ new_request:
 	BUG_ON(ceph_wbc->op_idx + 1 != req->r_num_ops);
 
 	ceph_wbc->from_pool = false;
-	if (i < ceph_wbc->locked_pages) {
+	if (processed_pages < ceph_wbc->locked_pages) {
 		BUG_ON(ceph_wbc->num_ops <= req->r_num_ops);
 		ceph_wbc->num_ops -= req->r_num_ops;
-		ceph_wbc->locked_pages -= i;
+		ceph_wbc->locked_pages -= processed_pages;
 
 		/* allocate new pages array for next request */
 		ceph_wbc->data_pages = ceph_wbc->pages;
 		__ceph_allocate_page_array(ceph_wbc, ceph_wbc->locked_pages);
-		memcpy(ceph_wbc->pages, ceph_wbc->data_pages + i,
+		memcpy(ceph_wbc->pages, ceph_wbc->data_pages + processed_pages,
 			ceph_wbc->locked_pages * sizeof(*ceph_wbc->pages));
-		memset(ceph_wbc->data_pages + i, 0,
+		memset(ceph_wbc->data_pages + processed_pages, 0,
 			ceph_wbc->locked_pages * sizeof(*ceph_wbc->pages));
 	} else {
 		BUG_ON(ceph_wbc->num_ops != req->r_num_ops);
@@ -1583,7 +1591,7 @@ new_request:
 	ceph_osdc_start_request(&fsc->client->osdc, req);
 	req = NULL;
 
-	wbc->nr_to_write -= i;
+	wbc->nr_to_write -= processed_pages;
 	if (ceph_wbc->pages)
 		goto new_request;