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
Fixes: 82cae269cfa9 ("fs/ntfs3: Add initialization of super block")
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Reported-by: syzbot+1631f09646bc214d2e76@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Konstantin Komarov <almaz.alexandrovich@xxxxxxxxxxxxxxxxxxxx>
Cc: ntfs3@xxxxxxxxxxxxxxx
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Kari Argillander <kari.argillander@xxxxxxxxxxxxxxxxxxxx>
Cc: Namjae Jeon <linkinjeon@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
---
v2: use Willy's suggestions
v3: use Namjae's suggestions -- but now Konstantin can decide.
drop Willy's Rev-by: tag due to changes
fs/ntfs3/super.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
--- linux-next-20220428.orig/fs/ntfs3/super.c
+++ linux-next-20220428/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;
