[lvc-project] [PATCH] f2fs: fix several potential integer overflows in file offsets

[Nikita Zhandarovich]

When dealing with large extents and calculating file offsets by
summing up according extent offsets and lengths of unsigned int type,
one may encounter possible integer overflow if the values are
big enough.

Prevent this from happening by expanding one of the addends to
(pgoff_t) type.

Found by Linux Verification Center (linuxtesting.org) with static
analysis tool SVACE.

Fixes: d323d005ac4a ("f2fs: support file defragment")
Cc: stable at vger.kernel.org
Signed-off-by: Nikita Zhandarovich <n.zhandarovich at fintech.ru>
---
As the patch covers several code fragments, one singular Fixes: tag
is hard to pinpoint. Hopefully, it's not critical at this stage.

 fs/f2fs/extent_cache.c | 4 ++--
 fs/f2fs/file.c         | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index fd1fc06359ee..62ac440d9416 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -366,7 +366,7 @@ static unsigned int __free_extent_tree(struct f2fs_sb_info *sbi,
 static void __drop_largest_extent(struct extent_tree *et,
 					pgoff_t fofs, unsigned int len)
 {
-	if (fofs < et->largest.fofs + et->largest.len &&
+	if (fofs < (pgoff_t)et->largest.fofs + et->largest.len &&
 			fofs + len > et->largest.fofs) {
 		et->largest.len = 0;
 		et->largest_updated = true;
@@ -456,7 +456,7 @@ static bool __lookup_extent_tree(struct inode *inode, pgoff_t pgofs,
 
 	if (type == EX_READ &&
 			et->largest.fofs <= pgofs &&
-			et->largest.fofs + et->largest.len > pgofs) {
+			(pgoff_t)et->largest.fofs + et->largest.len > pgofs) {
 		*ei = et->largest;
 		ret = true;
 		stat_inc_largest_node_hit(sbi);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 168f08507004..c598cfe5e0ed 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -2710,7 +2710,7 @@ static int f2fs_defragment_range(struct f2fs_sb_info *sbi,
 	 * block addresses are continuous.
 	 */
 	if (f2fs_lookup_read_extent_cache(inode, pg_start, &ei)) {
-		if (ei.fofs + ei.len >= pg_end)
+		if ((pgoff_t)ei.fofs + ei.len >= pg_end)
 			goto out;
 	}