From 111f8d74a19d85942ecbb3aba78f6f3c88e59391 Mon Sep 17 00:00:00 2001 From: Weiming Shi Date: Tue, 23 Jun 2026 03:14:35 -0700 Subject: [PATCH] fs/ntfs3: reject restart table growth beyond U16_MAX entries During $LogFile replay, log_replay() indexes the transaction table by the transact_id taken from the log record header. check_log_rec() only verifies that transact_id is non-zero and properly aligned, not its magnitude, so a crafted image can request an arbitrarily large index. alloc_rsttbl_from_idx() grows the table to cover that index via extend_rsttbl(), which passes the new entry count to init_rsttbl(): rt = init_rsttbl(esize, used + add); used + add is computed as u32 but init_rsttbl() takes a u16, and the count is stored in struct RESTART_TABLE as a __le16. When used + add exceeds U16_MAX it is truncated, init_rsttbl() allocates a table far smaller than the index requires, and alloc_rsttbl_from_idx() then dereferences and writes at the original, untruncated offset -- an out-of-bounds access past the allocation, reachable by mounting a crafted NTFS image. BUG: KASAN: use-after-free in alloc_rsttbl_from_idx (fs/ntfs3/fslog.c:950) Read of size 4 at addr ffff8880327ffff8 by task exploit alloc_rsttbl_from_idx (fs/ntfs3/fslog.c:950) log_replay (fs/ntfs3/fslog.c:4562) ntfs_loadlog_and_replay (fs/ntfs3/fsntfs.c:324) ntfs_fill_super (fs/ntfs3/super.c:1393) get_tree_bdev_flags vfs_get_tree path_mount __x64_sys_mount A restart table is limited to U16_MAX entries by its __le16 count, so a larger growth request is invalid input. Reject it in extend_rsttbl(); all callers already handle a NULL return. Fixes: b46acd6a6a62 ("fs/ntfs3: Add NTFS journal") Reported-by: Xiang Mei Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Weiming Shi Signed-off-by: Konstantin Komarov --- fs/ntfs3/fslog.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/ntfs3/fslog.c b/fs/ntfs3/fslog.c index cc24c23e4db9..ab210c33f770 100644 --- a/fs/ntfs3/fslog.c +++ b/fs/ntfs3/fslog.c @@ -853,6 +853,9 @@ static inline struct RESTART_TABLE *extend_rsttbl(struct RESTART_TABLE *tbl, u32 used = le16_to_cpu(tbl->used); struct RESTART_TABLE *rt; + if (used + add > U16_MAX) + return NULL; + rt = init_rsttbl(esize, used + add); if (!rt) return NULL;