[Qemu-devel] [PATCH] bitmap: assert that start and nr are non negative

[Peter Lieven <pl@kamp.de>]

commit e1123a3b introduced a data corruption regression
in the iscsi driver because it passed -1 as nr to bitmap_set
and bitmap_clear. Add an assertion to catch such flaws earlier.

Suggested-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Peter Lieven <pl@kamp.de>
---
 util/bitmap.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/util/bitmap.c b/util/bitmap.c
index 43ed011..c1a84ca 100644
--- a/util/bitmap.c
+++ b/util/bitmap.c
@@ -164,6 +164,8 @@ void bitmap_set(unsigned long *map, long start, long nr)
     int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
     unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
 
+    assert(start >= 0 && nr >= 0);
+
     while (nr - bits_to_set >= 0) {
         *p |= mask_to_set;
         nr -= bits_to_set;
@@ -184,6 +186,8 @@ void bitmap_set_atomic(unsigned long *map, long start, long nr)
     int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
     unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
 
+    assert(start >= 0 && nr >= 0);
+
     /* First word */
     if (nr - bits_to_set > 0) {
         atomic_or(p, mask_to_set);
@@ -221,6 +225,8 @@ void bitmap_clear(unsigned long *map, long start, long nr)
     int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
     unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
 
+    assert(start >= 0 && nr >= 0);
+
     while (nr - bits_to_clear >= 0) {
         *p &= ~mask_to_clear;
         nr -= bits_to_clear;
@@ -243,6 +249,8 @@ bool bitmap_test_and_clear_atomic(unsigned long *map, long start, long nr)
     unsigned long dirty = 0;
     unsigned long old_bits;
 
+    assert(start >= 0 && nr >= 0);
+
     /* First word */
     if (nr - bits_to_clear > 0) {
         old_bits = atomic_fetch_and(p, ~mask_to_clear);
-- 
1.9.1