[PATCH] read-cache: fix index corruption with index v4
- From
Thomas Gummerer <t.gummerer@gmail.com>
- Date
- Sep 4, 2017, 22:58 UTC
- Message-ID
- <20170904225807.22139-1-t.gummerer@gmail.com>
ce012deb98 ("read-cache: avoid allocating every ondisk entry when writing", 2017-08-21) changed the way cache entries are written to the index file. While previously it wrote the name to an struct that was allocated using xcalloc(), it now uses ce_write() directly. Previously ce_namelen - common bytes were written to the cache entry, which would automatically make it nul terminated, as it was allocated using calloc.
Now we are writing ce_namelen - common + 1 bytes directly from the ce->name to the index. As ce->name is however not nul terminated, and index-v4 needs the nul terminator to split between one index entry and the next, this would end up in a corrupted index.
Fix that by only writing ce_namelen - common bytes directly from ce->name to the index, and adding the nul terminator in an extra call to ce_write.
This bug was turned up by setting TEST_GIT_INDEX_VERSION = 4 in config.mak and running the test suite (t1700 specifically broke).
Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com> ---
I unfortunately didn't have more time to dig so
> As ce->name is however not nul terminated
just comes from my memory and from the patch below actually fixing the corruption, so it's really the most likely cause. Would be great if someone who can remember more about the index could confirm that this is indeed the case.
read-cache.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/read-cache.c b/read-cache.c index 40da87ea71..80830ddcfc 100644 --- a/read-cache.c +++ b/read-cache.c @@ -2103,7 +2103,9 @@ static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce, if (!result) result = ce_write(c, fd, to_remove_vi, prefix_size); if (!result) - result = ce_write(c, fd, ce->name + common, ce_namelen(ce) - common + 1); + result = ce_write(c, fd, ce->name + common, ce_namelen(ce) - common); + if (!result) + result = ce_write(c, fd, "\0", 1); strbuf_splice(previous_name, common, to_remove, ce->name + common, ce_namelen(ce) - common);
-- 2.14.1.480.gb18f417b89