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authorVitaly Kuznetsov <vkuznets@redhat.com>2015-09-17 16:01:51 -0700
committerSasha Levin <sasha.levin@oracle.com>2016-02-03 16:23:21 -0500
commit4aba5827e764110bd1462eecf79209e656090f9c (patch)
treee43253d82584cc7a1b2803a59ffdf17d0f9f88c0
parent3730198645d95e2ac438ea9276402d3908b9449d (diff)
lib/string_helpers.c: fix infinite loop in string_get_size()
[ 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@redhat.com> Acked-by: James Bottomley <JBottomley@Odin.com> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
-rw-r--r--lib/string_helpers.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index c98ae818eb4e..bbf1bef7d7ee 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++;