From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
This patch has been added to the 4.1 stable tree. If you have any
objections, please let us know.
===============
[ Upstream commit 62bef58a55dfa8ada2a22b2496c6340468ecd98a ]
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.
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Acked-by: James Bottomley <JBottomley@xxxxxxxx>
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
lib/string_helpers.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index c98ae81..bbf1bef 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -59,7 +59,11 @@ void string_get_size(u64 size, u64 blk_size, const enum string_size_units units,
}
exp = divisor[units] / (u32)blk_size;
- if (size >= exp) {
+ /*
+ * size must be strictly greater than exp here to ensure that remainder
+ * is greater than divisor[units] coming out of the if below.
+ */
+ if (size > exp) {
remainder = do_div(size, divisor[units]);
remainder *= blk_size;
i++;
--
2.5.0
--
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