[PATCH 5/6] load_contents(): don't try to mmap an empty file
- From
Michael Haggerty <mhagger@alum.mit.edu>
- Date
- Jan 24, 2018, 11:14 UTC
- Message-ID
- <f06611f06a8b01843bd71cd9fedec0f1eb0ee551.1516791909.git.mhagger@alum.mit.edu>
- In-Reply-To
- <cea5e366-dc95-6f41-6373-f8bbef103561@alum.mit.edu>
We don't actually create zero-length `packed-refs` files, but they are valid and we should handle them correctly. The old code `xmmap()`ed such files, which led to an error when `munmap()` was called. So, if the `packed-refs` file is empty, leave the snapshot at its zero values and return 0 without trying to read or mmap the file.
Returning 0 also makes `create_snapshot()` exit early, which avoids the technically undefined comparison `NULL < NULL`.
Reported-by: Kim Gybels <kgybels@infogroep.be> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> --- refs/packed-backend.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/refs/packed-backend.c b/refs/packed-backend.c index 988c45402b..e829cf206d 100644 --- a/refs/packed-backend.c +++ b/refs/packed-backend.c @@ -461,7 +461,8 @@ static void verify_buffer_safe(struct snapshot *snapshot) /* * Depending on `mmap_strategy`, either mmap or read the contents of * the `packed-refs` file into the snapshot. Return 1 if the file - * existed and was read, or 0 if the file was absent. Die on errors. + * existed and was read, or 0 if the file was absent or empty. Die on + * errors. */ static int load_contents(struct snapshot *snapshot) { @@ -492,19 +493,17 @@ static int load_contents(struct snapshot *snapshot) die_errno("couldn't stat %s", snapshot->refs->path); size = xsize_t(st.st_size); - switch (mmap_strategy) { - case MMAP_NONE: + if (!size) { + return 0; + } else if (mmap_strategy == MMAP_NONE) { snapshot->buf = xmalloc(size); bytes_read = read_in_full(fd, snapshot->buf, size); if (bytes_read < 0 || bytes_read != size) die_errno("couldn't read %s", snapshot->refs->path); snapshot->mmapped = 0; - break; - case MMAP_TEMPORARY: - case MMAP_OK: + } else { snapshot->buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0); snapshot->mmapped = 1; - break; } close(fd);
-- 2.14.2