The existing implementation of range_set_union does not correctly
reallocate memory, leading to a heap overflow when it attempts to union
more than 24 separate line ranges.
For struct range_set *out to grow correctly it must have out->nr set to
the current size of the buffer when it is passed to range_set_grow.
However, the existing implementation of range_set_union only updates
out->nr at the end of the function, meaning that it is always zero
before this. This results in range_set_grow never growing the buffer, as
well as some of the union logic itself being incorrect as !out->nr is
always true.
The reason why 24 is the limit is that the first allocation of size 1
ends up allocating a buffer of size 24 (due to the call to alloc_nr in
ALLOC_GROW). This goes some way to explain why this hasn't been
caught before.
Fix the problem by correctly updating out->nr after reallocating the
range_set. As this results in out->nr containing the same value as the
variable o, replace o with out->nr as well.
Finally, add a new test to help prevent the problem reoccurring in the
future. Thanks to Vegard Nossum for writing the test.
Signed-off-by: Allan Xavier <allan.x.xavier@xxxxxxxxxx>
---
Originally sent to git-security@xxxxxxxxxxxxxxxx to give hosted
services a chance to apply this if they were affected.
line-log.c | 15 +++++++--------
t/t4211-line-log.sh | 10 ++++++++++
2 files changed, 17 insertions(+), 8 deletions(-)
diff --git a/line-log.c b/line-log.c
index 65f3558b3..951029665 100644
--- a/line-log.c
+++ b/line-log.c
@@ -144,7 +144,7 @@ void sort_and_merge_range_set(struct range_set *rs)
static void range_set_union(struct range_set *out,
struct range_set *a, struct range_set *b)
{
- int i = 0, j = 0, o = 0;
+ int i = 0, j = 0;
struct range *ra = a->ranges;
struct range *rb = b->ranges;
/* cannot make an alias of out->ranges: it may change during grow */
@@ -167,16 +167,15 @@ static void range_set_union(struct range_set *out,
new = &rb[j++];
if (new->start == new->end)
; /* empty range */
- else if (!o || out->ranges[o-1].end < new->start) {
+ else if (!out->nr || out->ranges[out->nr-1].end < new->start) {
range_set_grow(out, 1);
- out->ranges[o].start = new->start;
- out->ranges[o].end = new->end;
- o++;
- } else if (out->ranges[o-1].end < new->end) {
- out->ranges[o-1].end = new->end;
+ out->ranges[out->nr].start = new->start;
+ out->ranges[out->nr].end = new->end;
+ out->nr++;
+ } else if (out->ranges[out->nr-1].end < new->end) {
+ out->ranges[out->nr-1].end = new->end;
}
}
- out->nr = o;
}
/*
diff --git a/t/t4211-line-log.sh b/t/t4211-line-log.sh
index 9d87777b5..d0377fae5 100755
--- a/t/t4211-line-log.sh
+++ b/t/t4211-line-log.sh
@@ -106,4 +106,14 @@ test_expect_success '-L with --output' '
test_line_count = 70 log
'
+test_expect_success 'range_set_union' '
+ test_seq 500 > c.c &&
+ git add c.c &&
+ git commit -m "many lines" &&
+ test_seq 1000 > c.c &&
+ git add c.c &&
+ git commit -m "modify many lines" &&
+ git log $(for x in $(test_seq 200); do echo -L $((2*x)),+1:c.c; done)
+'
+
test_done
--
2.11.0