[PATCH 5.15 47/66] fs/ntfs3: validate BOOT sectors_per_clusters

Greg Kroah-Hartman
2022-06-03T18:01:08Z

From: Randy Dunlap <rdunlap@infradead.org>

commit a3b774342fa752a5290c0de36375289dfcf4a260 upstream.

When the NTFS BOOT sectors_per_clusters field is > 0x80, it represents a
shift value. Make sure that the shift value is not too large before using
it (NTFS max cluster size is 2MB). Return -EVINVAL if it too large.

This prevents negative shift values and shift values that are larger than
the field size.

Prevents this UBSAN error:

UBSAN: shift-out-of-bounds in ../fs/ntfs3/super.c:673:16
shift exponent -192 is negative

Link: https://lkml.kernel.org/r/20220502175342.20296-1-rdunlap@infradead.org
Fixes: 82cae269cfa9 ("fs/ntfs3: Add initialization of super block")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: syzbot+1631f09646bc214d2e76@syzkaller.appspotmail.com
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Kari Argillander <kari.argillander@stargateuniverse.net>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ntfs3/super.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -668,9 +668,11 @@ static u32 format_size_gb(const u64 byte

static u32 true_sectors_per_clst(const struct NTFS_BOOT *boot)
{
- return boot->sectors_per_clusters <= 0x80
- ? boot->sectors_per_clusters
- : (1u << (0 - boot->sectors_per_clusters));
+ if (boot->sectors_per_clusters <= 0x80)
+ return boot->sectors_per_clusters;
+ if (boot->sectors_per_clusters >= 0xf4) /* limit shift to 2MB max */
+ return 1U << (0 - boot->sectors_per_clusters);
+ return -EINVAL;
}

/*
@@ -713,6 +715,8 @@ static int ntfs_init_from_boot(struct su

/* cluster size: 512, 1K, 2K, 4K, ... 2M */
sct_per_clst = true_sectors_per_clst(boot);
+ if ((int)sct_per_clst < 0)
+ goto out;
if (!is_power_of_2(sct_per_clst))
goto out;