CVE-2026-90200

In the Linux kernel, the following vulnerability has been resolved:

fs/ntfs3: fix integer overflow in MFT cluster validation

In ntfs_init_from_boot(), the boot sector's MFT cluster numbers are

validated against the volume size with:

if (mlcn * sct_per_clst >= sectors ||

mlcn2 * sct_per_clst >= sectors)

goto out;

mlcn and mlcn2 are u64 fields read directly from the boot sector.

sct_per_clst is bounded above by 4096 (true_sectors_per_clst() plus

the is_power_of_2() check below it), but the multiplication is done

in u64 and wraps when mlcn (or mlcn2) is large enough -- e.g. mlcn

near 2^62 with sct_per_clst == 4 wraps to 0, which compares below

any non-zero 'sectors', so the check is bypassed and the malformed

record is accepted.

The accepted mlcn is then used unchanged in

sbi->mft.lbo = mlcn << cluster_bits;

In practice the resulting reads fail at the block layer (sb_bread()

returns NULL via grow_buffers()'s check_mul_overflow() guard), so

today this manifests as mount failing in odd places rather than as

something more dangerous, but the validation step is still wrong

and there is no reason for callers to rely on the block layer to

catch a value that should never have been accepted in the first

place.

Use check_mul_overflow() to compute the two sector positions and

fail the mount if either multiplication wraps; this preserves the

existing semantics (mlcn * sct_per_clst >= sectors) instead of

switching to division (mlcn >= sectors / sct_per_clst), which

would tighten the check at edge cases where 'sectors' is not a

multiple of sct_per_clst. The check_*_overflow() style is the

one ntfs3 already uses for similar on-disk arithmetic in

fs/ntfs3/run.c.