diff options
| author | Vitaly Kuznetsov <vkuznets@redhat.com> | 2015-09-17 16:01:51 -0700 |
|---|---|---|
| committer | Sasha Levin <sasha.levin@oracle.com> | 2016-02-03 16:23:21 -0500 |
| commit | 4aba5827e764110bd1462eecf79209e656090f9c (patch) | |
| tree | e43253d82584cc7a1b2803a59ffdf17d0f9f88c0 /lib | |
| parent | 3730198645d95e2ac438ea9276402d3908b9449d (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>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/string_helpers.c | 6 |
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++; |