From de603b9d377fab57a5e6432fa84a9f36b32c1636 Mon Sep 17 00:00:00 2001 From: Konstantin Komarov Date: Tue, 4 Aug 2026 15:01:43 +0200 Subject: [PATCH] fs/ntfs3: fix out-of-bounds read in read_log_rec_buf() read_log_rec_buf() copies a log record into a caller buffer starting at u32 off = lsn_to_page_off(log, lsn) + log->record_header_len; log->record_header_len (and log->data_off, used for the following pages) comes verbatim from the on-disk restart area and is only checked for 8-byte alignment in is_rst_area_valid(), so off can exceed log->page_size. "tail = log->page_size - off" then underflows and memcpy() reads past the page_size-sized buffer returned by read_log_page(), spilling adjacent slab memory into the replay buffer. This is reachable by mounting a crafted NTFS image: BUG: KASAN: slab-out-of-bounds in read_log_rec_buf+0x216/0x580 Read of size 64 at addr ffff88800a877ff8 by task exploit/127 read_log_rec_buf fs/ntfs3/fslog.c:2299 log_replay fs/ntfs3/fslog.c:4216 ntfs_loadlog_and_replay fs/ntfs3/fsntfs.c:324 ntfs_fill_super fs/ntfs3/super.c:1392 get_tree_bdev_flags fs/super.c:1694 __x64_sys_mount fs/namespace.c:4360 The buggy address is located 4088 bytes to the right of the 4096-byte region [ffff88800a876000, ffff88800a877000) Reject an in-page offset outside the current page before the copy. Fixes: b46acd6a6a62 ("fs/ntfs3: Add NTFS journal") Assisted-by: Claude:claude-opus-4-8 Reported-by: Xiang Mei Signed-off-by: Weiming Shi [almaz.alexandrovich@paragon-software.com: replaced the >= sign with >] Signed-off-by: Konstantin Komarov --- fs/ntfs3/fslog.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/ntfs3/fslog.c b/fs/ntfs3/fslog.c index a7cddce30136..ed50c1d0c23e 100644 --- a/fs/ntfs3/fslog.c +++ b/fs/ntfs3/fslog.c @@ -2301,7 +2301,15 @@ static int read_log_rec_buf(struct ntfs_log *log, */ for (;;) { bool usa_error; - u32 tail = log->page_size - off; + u32 tail; + + /* off comes from the on-disk restart area; bound it. */ + if (off > log->page_size) { + err = -EINVAL; + goto out; + } + + tail = log->page_size - off; if (tail >= data_len) tail = data_len;