fs/ntfs3: validate BOOT sectors_per_clusters

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>

diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
index 278dcf502410231b3af89241b9cc0eef0af382db..b2b54c4553f916011900c4a1c726aa7c11d7ab90 100644 (file)
--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -668,9 +668,11 @@ static u32 format_size_gb(const u64 bytes, u32 *mb)
 
 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 super_block *sb, u32 sector_size,
 
        /* 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;