> On Mon, Jan 25, 2021 at 09:33:14AM -0800, syzbot wrote: > > UBSAN: shift-out-of-bounds in fs/exfat/super.c:471:28 shift exponent > > 4294967294 is too large for 32-bit type 'int' > > This is an integer underflow: > > sbi->dentries_per_clu = 1 << > (sbi->cluster_size_bits - DENTRY_SIZE_BITS); > > I think the problem is that there is no validation of sect_per_clus_bits. > We should check it is at least DENTRY_SIZE_BITS and probably that it's less than ... 16? 64? I don't > know what legitimate values are in this field, but I would imagine that 255 is completely unacceptable. exfat specification describe sect_per_clus_bits field of boot sector could be at most 32 and at least 0. And sect_size_bits can also affect this calculation, It also needs validation. I will fix it. Thanks!
