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authorJeff King <peff@peff.net>2018-06-15 03:31:13 (GMT)
committerJunio C Hamano <gitster@pobox.com>2018-06-18 16:13:57 (GMT)
commit9d2e330b1795222c2c816afa46138e7ff4ebec8e (patch)
tree615745f2611f52e42bf28137ab9594fd773a3523 /ewah/ewok.h
parenta42a58d7b62cc1d6301440e81a83feed9d7c118c (diff)
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ewah_read_mmap: bounds-check mmap reads
The on-disk ewah format tells us how big the ewah data is, and we blindly read that much from the buffer without considering whether the mmap'd data is long enough, which can lead to out-of-bound reads. Let's make sure we have data available before reading it, both for the ewah header/footer as well as for the bit data itself. In particular: - keep our ptr/len pair in sync as we move through the buffer, and check it before each read - check the size for integer overflow (this should be impossible on 64-bit, as the size is given as a 32-bit count of 8-byte words, but is possible on a 32-bit system) - return the number of bytes read as an ssize_t instead of an int, again to prevent integer overflow - compute the return value using a pointer difference; this should yield the same result as the existing code, but makes it more obvious that we got our computations right The included test is far from comprehensive, as it just picks a static point at which to truncate the generated bitmap. But in practice this will hit in the middle of an ewah and make sure we're at least exercising this code. Reported-by: Luat Nguyen <root@l4w.io> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'ewah/ewok.h')
-rw-r--r--ewah/ewok.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/ewah/ewok.h b/ewah/ewok.h
index dc43d05..357fd93 100644
--- a/ewah/ewok.h
+++ b/ewah/ewok.h
@@ -91,7 +91,7 @@ int ewah_serialize_native(struct ewah_bitmap *self, int fd);
int ewah_serialize_strbuf(struct ewah_bitmap *self, struct strbuf *);
int ewah_deserialize(struct ewah_bitmap *self, int fd);
-int ewah_read_mmap(struct ewah_bitmap *self, const void *map, size_t len);
+ssize_t ewah_read_mmap(struct ewah_bitmap *self, const void *map, size_t len);
uint32_t ewah_checksum(struct ewah_bitmap *self);