From: Shigeru Yoshida <syoshida@xxxxxxxxxx> [ Upstream commit caad9dd8792a2622737b7273cb34835fd9536cd2 ] syzbot reported UBSAN error as below: [ 76.901829][ T6677] ================================================================================ [ 76.903908][ T6677] UBSAN: shift-out-of-bounds in fs/ntfs3/super.c:675:13 [ 76.905363][ T6677] shift exponent -247 is negative This patch avoid this error. Link: https://syzkaller.appspot.com/bug?id=b0299c09a14aababf0f1c862dd4ebc8ab9eb0179 Fixes: a3b774342fa7 (fs/ntfs3: validate BOOT sectors_per_clusters) Cc: Author: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> Reported-by: syzbot+35b87c668935bb55e666@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Shigeru Yoshida <syoshida@xxxxxxxxxx> Signed-off-by: Konstantin Komarov <almaz.alexandrovich@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/ntfs3/super.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c index 47012c9bf505..adc4f73722b7 100644 --- a/fs/ntfs3/super.c +++ b/fs/ntfs3/super.c @@ -672,7 +672,7 @@ static u32 true_sectors_per_clst(const struct NTFS_BOOT *boot) 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 1U << -(s8)boot->sectors_per_clusters; return -EINVAL; } -- 2.35.1
