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authorStefano Brivio2020-08-11 18:34:29 -0700
committerLinus Torvalds2020-08-12 10:57:59 -0700
commit5959f829a93c18ccf15715768317b58f5d9bf2d4 (patch)
treef1db36913d2e4e8709848e6c70abe657d7144b75 /lib/bitmap.c
parent25fd529c34d063d1bef23742f2e8f8341c639dc3 (diff)
lib/bitmap.c: fix bitmap_cut() for partial overlapping case
Patch series "lib: Fix bitmap_cut() for overlaps, add test" This patch (of 2): Yury Norov reports that bitmap_cut() will not produce the right outcome if src and dst partially overlap, with src pointing at some location after dst, because the memmove() affects src before we store the bits that we need to keep, that is, the bits preceding the cut -- as long as we the beginning of the cut is not aligned to a long. Fix this by storing those bits before the memmove(). Note that this is just a theoretical concern so far, as the only user of this function, pipapo_drop() from the nftables set back-end implemented in net/netfilter/nft_set_pipapo.c, always supplies entirely overlapping src and dst. Fixes: 2092767168f0 ("bitmap: Introduce bitmap_cut(): cut bits and shift remaining") Reported-by: Yury Norov <yury.norov@gmail.com> Signed-off-by: Stefano Brivio <sbrivio@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Pablo Neira Ayuso <pablo@netfilter.org> Link: http://lkml.kernel.org/r/cover.1592155364.git.sbrivio@redhat.com Link: http://lkml.kernel.org/r/003e38d4428cd6091ef00b5b03354f1bd7d9091e.1592155364.git.sbrivio@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/bitmap.c')
-rw-r--r--lib/bitmap.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/lib/bitmap.c b/lib/bitmap.c
index 0364452b1617..c13d859bc7ab 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -212,13 +212,13 @@ void bitmap_cut(unsigned long *dst, const unsigned long *src,
unsigned long keep = 0, carry;
int i;
- memmove(dst, src, len * sizeof(*dst));
-
if (first % BITS_PER_LONG) {
keep = src[first / BITS_PER_LONG] &
(~0UL >> (BITS_PER_LONG - first % BITS_PER_LONG));
}
+ memmove(dst, src, len * sizeof(*dst));
+
while (cut--) {
for (i = first / BITS_PER_LONG; i < len; i++) {
if (i < len - 1)