git: d78aee09c08b - stable/12 - ffs: Avoid out-of-bounds accesses in the fs_active bitmap

[Mark Johnston]

The branch stable/12 has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=d78aee09c08b575c9bbc4c90a92f6253dfd8fa3b

commit d78aee09c08b575c9bbc4c90a92f6253dfd8fa3b
Author:     Mark Johnston <markj at FreeBSD.org>
AuthorDate: 2020-12-23 16:13:00 +0000
Commit:     Mark Johnston <markj at FreeBSD.org>
CommitDate: 2021-01-06 14:43:22 +0000

    ffs: Avoid out-of-bounds accesses in the fs_active bitmap
    
    We use a bitmap to track which cylinder groups have changed between
    snapshot creation and filesystem suspension.  The "legs" of the bitmap
    are four bytes wide (see ACTIVESET()) so we must round up the allocation
    size to a multiple of four bytes.
    
    I believe this bug is harmless since UMA/kmem_* will both pad the
    allocation and zero the full allocation.  Note that malloc() does inline
    zeroing when the allocation size is known at compile-time.
    
    Reported by:    pho (using KASAN)
    Reviewed by:    kib, mckusick
    
    (cherry picked from commit ace3d9475ceecd9bcb766bb82a1c8f87e8f560be)
---
 sys/ufs/ffs/ffs_snapshot.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sys/ufs/ffs/ffs_snapshot.c b/sys/ufs/ffs/ffs_snapshot.c
index 3cb999a01c56..749ab28fab56 100644
--- a/sys/ufs/ffs/ffs_snapshot.c
+++ b/sys/ufs/ffs/ffs_snapshot.c
@@ -377,8 +377,8 @@ restart:
 	 * touch up the few cylinder groups that changed during
 	 * the suspension period.
 	 */
-	len = howmany(fs->fs_ncg, NBBY);
-	space = malloc(len, M_DEVBUF, M_WAITOK|M_ZERO);
+	len = roundup2(howmany(fs->fs_ncg, NBBY), sizeof(int));
+	space = malloc(len, M_DEVBUF, M_WAITOK | M_ZERO);
 	UFS_LOCK(ump);
 	fs->fs_active = space;
 	UFS_UNLOCK(ump);