From: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> [ Upstream commit 0afa9626667c3659ef8bd82d42a11e39fedf235c ] On corrupted FATfs may have invalid ->i_start. To handle it, this checks ->i_start before using, and return proper error code. Link: http://lkml.kernel.org/r/87o9f8y1t5.fsf_-_@xxxxxxxxxxxxxxxxxx Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> Reported-by: Anatoly Trosinenko <anatoly.trosinenko@xxxxxxxxx> Tested-by: Anatoly Trosinenko <anatoly.trosinenko@xxxxxxxxx> Cc: Alan Cox <gnomes@xxxxxxxxxxxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> --- fs/fat/cache.c | 19 ++++++++++++------- fs/fat/fat.h | 5 +++++ fs/fat/fatent.c | 6 +++--- 3 files changed, 20 insertions(+), 10 deletions(-) diff --git a/fs/fat/cache.c b/fs/fat/cache.c index 91ad9e1c9441..4c634b365516 100644 --- a/fs/fat/cache.c +++ b/fs/fat/cache.c @@ -226,7 +226,8 @@ static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus) int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus) { struct super_block *sb = inode->i_sb; - const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->cluster_bits; + struct msdos_sb_info *sbi = MSDOS_SB(sb); + const int limit = sb->s_maxbytes >> sbi->cluster_bits; struct fat_entry fatent; struct fat_cache_id cid; int nr; @@ -235,6 +236,12 @@ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus) *fclus = 0; *dclus = MSDOS_I(inode)->i_start; + if (!fat_valid_entry(sbi, *dclus)) { + fat_fs_error_ratelimit(sb, + "%s: invalid start cluster (i_pos %lld, start %08x)", + __func__, MSDOS_I(inode)->i_pos, *dclus); + return -EIO; + } if (cluster == 0) return 0; @@ -251,9 +258,8 @@ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus) /* prevent the infinite loop of cluster chain */ if (*fclus > limit) { fat_fs_error_ratelimit(sb, - "%s: detected the cluster chain loop" - " (i_pos %lld)", __func__, - MSDOS_I(inode)->i_pos); + "%s: detected the cluster chain loop (i_pos %lld)", + __func__, MSDOS_I(inode)->i_pos); nr = -EIO; goto out; } @@ -263,9 +269,8 @@ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus) goto out; else if (nr == FAT_ENT_FREE) { fat_fs_error_ratelimit(sb, - "%s: invalid cluster chain (i_pos %lld)", - __func__, - MSDOS_I(inode)->i_pos); + "%s: invalid cluster chain (i_pos %lld)", + __func__, MSDOS_I(inode)->i_pos); nr = -EIO; goto out; } else if (nr == FAT_ENT_EOF) { diff --git a/fs/fat/fat.h b/fs/fat/fat.h index e0c4ba39a377..add94f15d5be 100644 --- a/fs/fat/fat.h +++ b/fs/fat/fat.h @@ -347,6 +347,11 @@ static inline void fatent_brelse(struct fat_entry *fatent) fatent->fat_inode = NULL; } +static inline bool fat_valid_entry(struct msdos_sb_info *sbi, int entry) +{ + return FAT_START_ENT <= entry && entry < sbi->max_cluster; +} + extern void fat_ent_access_init(struct super_block *sb); extern int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry); diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c index 260705c58062..08b3db146888 100644 --- a/fs/fat/fatent.c +++ b/fs/fat/fatent.c @@ -26,7 +26,7 @@ static void fat12_ent_blocknr(struct super_block *sb, int entry, { struct msdos_sb_info *sbi = MSDOS_SB(sb); int bytes = entry + (entry >> 1); - WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry); + WARN_ON(!fat_valid_entry(sbi, entry)); *offset = bytes & (sb->s_blocksize - 1); *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits); } @@ -36,7 +36,7 @@ static void fat_ent_blocknr(struct super_block *sb, int entry, { struct msdos_sb_info *sbi = MSDOS_SB(sb); int bytes = (entry << sbi->fatent_shift); - WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry); + WARN_ON(!fat_valid_entry(sbi, entry)); *offset = bytes & (sb->s_blocksize - 1); *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits); } @@ -356,7 +356,7 @@ int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry) int err, offset; sector_t blocknr; - if (entry < FAT_START_ENT || sbi->max_cluster <= entry) { + if (!fat_valid_entry(sbi, entry)) { fatent_brelse(fatent); fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry); return -EIO; -- 2.17.1
