The patch titled
Subject: lib/string_helpers.c: fix infinite loop in string_get_size()
has been added to the -mm tree. Its filename is
lib-string_helpersc-fix-infinite-loop-in-string_get_size.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-string_helpersc-fix-infinite-loop-in-string_get_size.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-string_helpersc-fix-infinite-loop-in-string_get_size.patch
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From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Subject: 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 routing from
infinite looping.
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/string_helpers.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN lib/string_helpers.c~lib-string_helpersc-fix-infinite-loop-in-string_get_size lib/string_helpers.c
--- a/lib/string_helpers.c~lib-string_helpersc-fix-infinite-loop-in-string_get_size
+++ a/lib/string_helpers.c
@@ -59,7 +59,7 @@ void string_get_size(u64 size, u64 blk_s
}
exp = divisor[units] / (u32)blk_size;
- if (size >= exp) {
+ if (size > exp) {
remainder = do_div(size, divisor[units]);
remainder *= blk_size;
i++;
_
Patches currently in -mm which might be from vkuznets@xxxxxxxxxx are
lib-string_helpersc-fix-infinite-loop-in-string_get_size.patch
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