From 20dd3185d13865214ff25b0bf7b931e8d73be1ac Mon Sep 17 00:00:00 2001 From: David Timber Date: Sun, 12 Apr 2026 08:32:51 +0900 Subject: [PATCH] exfat: fix handling of damaged volume in exfat_create_upcase_table() When the size of the upcase table is set to zero in the dentry for any reason(e.g. corrupted media or misbehaving device), an integer overflow causes the module to loop indefinitely. If the size of the upcase table is read zero, do not attempt to load the table. Instead, fallback to loading the default upcase table. If the size of the upcase table is zero or no upcase table is found, raise exfat_fs_error() to mark the volume read-only. Signed-off-by: David Timber Signed-off-by: Namjae Jeon --- fs/exfat/nls.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/fs/exfat/nls.c b/fs/exfat/nls.c index 57db08a5271c..055447edcf9a 100644 --- a/fs/exfat/nls.c +++ b/fs/exfat/nls.c @@ -769,13 +769,18 @@ int exfat_create_upcase_table(struct super_block *sb) tbl_clu = le32_to_cpu(ep->dentry.upcase.start_clu); tbl_size = le64_to_cpu(ep->dentry.upcase.size); - - sector = exfat_cluster_to_sector(sbi, tbl_clu); - num_sectors = ((tbl_size - 1) >> blksize_bits) + 1; - ret = exfat_load_upcase_table(sb, sector, num_sectors, - le32_to_cpu(ep->dentry.upcase.checksum)); - + if (tbl_size) { + sector = exfat_cluster_to_sector(sbi, tbl_clu); + num_sectors = ((tbl_size - 1) >> blksize_bits) + 1; + ret = exfat_load_upcase_table(sb, sector, num_sectors, + le32_to_cpu(ep->dentry.upcase.checksum)); + } else { + exfat_fs_error(sb, + "bad upcase table size (0 bytes). Please run fsck"); + ret = -EINVAL; + } brelse(bh); + if (ret && ret != -EIO) { /* free memory from exfat_load_upcase_table call */ exfat_free_upcase_table(sbi); @@ -790,6 +795,8 @@ int exfat_create_upcase_table(struct super_block *sb) return -EIO; } + exfat_fs_error(sb, "no upcase table entry. Please run fsck"); + load_default: /* load default upcase table */ return exfat_load_default_upcase_table(sb);