From aaae0bf787f09ba102f69c3cf85d37e6554ab9fd Mon Sep 17 00:00:00 2001 From: Allan Xavier Date: Thu, 2 Mar 2017 17:29:02 +0000 Subject: line-log.c: prevent crash during union of too many ranges 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 Reviewed-by: Jeff King Signed-off-by: Junio C Hamano --- line-log.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) (limited to 'line-log.c') diff --git a/line-log.c b/line-log.c index 916e724870..47eaba73c6 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; } /* -- cgit v1.2.1