exfat: fix overflow issue in exfat_cluster_to_sector()

namjaejeon · namjaejeon · commit 9cbc7e418ed0 · 2020-07-03T13:41:34.000+09:00
An overflow issue can occur at sector calculation in
exfat_cluster_to_sector(). It needs to cast clus's type to sector_t
before left shifting.

Signed-off-by: Namjae Jeon &lt;linkinjeon@kernel.org&gt;
diff --git a/exfat_fs.h b/exfat_fs.h
@@ -381,7 +381,7 @@ static inline bool exfat_is_last_sector_in_cluster(struct exfat_sb_info *sbi,
 static inline sector_t exfat_cluster_to_sector(struct exfat_sb_info *sbi,
 		unsigned int clus)
 {
-	return ((clus - EXFAT_RESERVED_CLUSTERS) << sbi->sect_per_clus_bits) +
+	return ((sector_t)(clus - EXFAT_RESERVED_CLUSTERS) << sbi->sect_per_clus_bits) +
 		sbi->data_start_sector;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -381,7 +381,7 @@ static inline bool exfat_is_last_sector_in_cluster(struct exfat_sb_info *sbi,`
`381`	`381`	`static inline sector_t exfat_cluster_to_sector(struct exfat_sb_info *sbi,`
`382`	`382`	`unsigned int clus)`
`383`	`383`	`{`
`384`		`- return ((clus - EXFAT_RESERVED_CLUSTERS) << sbi->sect_per_clus_bits) +`
	`384`	`+ return ((sector_t)(clus - EXFAT_RESERVED_CLUSTERS) << sbi->sect_per_clus_bits) +`
`385`	`385`	`sbi->data_start_sector;`
`386`	`386`	`}`
`387`	`387`