lib/string_helpers.c: fix infinite loop in string_get_size()

Some string_get_size() calls (e.g.: string_get_size(1, 512, STRING_UNITS_10, ..., ...) string_get_size(15, 64, STRING_UNITS_10, ..., ...) ) result in an infinite loop. The problem is that if size is equal to divisor[units]/blk_size and is smaller than divisor[units] we'll end up with size == 0 when we start doing sf_cap calculations: For string_get_size(1, 512, STRING_UNITS_10, ..., ...) case: ... remainder = do_div(size, divisor[units]); -> size is 0, remainder is 1 remainder *= blk_size; -> remainder is 512 ... size *= blk_size; -> size is still 0 size += remainder / divisor[units]; -> size is still 0 The caller causing the issue is sd_read_capacity(), the problem was noticed on Hyper-V, such weird size was reported by host when scanning collides with device removal. This is probably a separate issue worth fixing, this patch is intended to prevent the library routine from infinite looping.

Vitaly Kuznetsov committed 11 years ago

Commit 62bef581 parent 14b97de1 file · +5 −1Browse files

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lib/string_helpers.c+5−1

@@ -59,7 +59,11 @@ void string_get_size(u64 size, u64 blk_size, const enum string_size_units units, · 58 unmodified lines
59	59	}
60	60
61	61	exp = divisor[units] / (u32)blk_size;
62		− if (size >= exp) {
	62	+ /*
	63	+ * size must be strictly greater than exp here to ensure that remainder
	64	+ * is greater than divisor[units] coming out of the if below.
	65	+ */
	66	+ if (size > exp) {
63	67	remainder = do_div(size, divisor[units]);
64	68	remainder *= blk_size;
65	69	i++;