[PATCH 6.12 164/567] fs/ntfs3: fix mount failure for sparse runs in run_unpack()

Greg Kroah-Hartman
2026-01-06T17:23:20Z

From: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

commit 801f614ba263cb37624982b27b4c82f3c3c597a9 upstream.

Some NTFS volumes failed to mount because sparse data runs were not
handled correctly during runlist unpacking. The code performed arithmetic
on the special SPARSE_LCN64 marker, leading to invalid LCN values and
mount errors.

Add an explicit check for the case described above, marking the run as
sparse without applying arithmetic.

Fixes: 736fc7bf5f68 ("fs: ntfs3: Fix integer overflow in run_unpack()")
Cc: stable@vger.kernel.org
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ntfs3/run.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/fs/ntfs3/run.c
+++ b/fs/ntfs3/run.c
@@ -984,8 +984,12 @@ int run_unpack(struct runs_tree *run, st
if (!dlcn)
return -EINVAL;

- if (check_add_overflow(prev_lcn, dlcn, &lcn))
+ /* Check special combination: 0 + SPARSE_LCN64. */
+ if (!prev_lcn && dlcn == SPARSE_LCN64) {
+ lcn = SPARSE_LCN64;
+ } else if (check_add_overflow(prev_lcn, dlcn, &lcn)) {
return -EINVAL;
+ }
prev_lcn = lcn;
} else {
/* The size of 'dlcn' can't be > 8. */