From: Jeff King <peff@peff.net>
To: git@vger.kernel.org
Cc: Jonathan Nieder <jrnieder@gmail.com>, Junio C Hamano <gitster@pobox.com>
Subject: [PATCH v2 4/7] avoid looking at errno for short read_in_full() returns
Date: Wed, 27 Sep 2017 02:01:07 -0400 [thread overview]
Message-ID: <20170927060107.duocwl3mf62zvgjp@sigill.intra.peff.net> (raw)
In-Reply-To: <20170927055424.22ati3g24xaqtqrk@sigill.intra.peff.net>
When a caller tries to read a particular set of bytes via
read_in_full(), there are three possible outcomes:
1. An error, in which case -1 is returned and errno is
set.
2. A short read, in which fewer bytes are returned and
errno is unspecified (we never saw a read error, so we
may have some random value from whatever syscall failed
last).
3. The full read completed successfully.
Many callers handle cases 1 and 2 together by just checking
the result against the requested size. If their combined
error path looks at errno (e.g., by calling die_errno), they
may report a nonsense value.
Let's fix these sites by having them distinguish between the
two error cases. That avoids the random errno confusion, and
lets us give more detailed error messages.
Signed-off-by: Jeff King <peff@peff.net>
---
pack-write.c | 7 ++++++-
sha1_file.c | 11 ++++++++---
2 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/pack-write.c b/pack-write.c
index a333ec6754..fea6284192 100644
--- a/pack-write.c
+++ b/pack-write.c
@@ -213,14 +213,19 @@ void fixup_pack_header_footer(int pack_fd,
git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
struct pack_header hdr;
char *buf;
+ ssize_t read_result;
git_SHA1_Init(&old_sha1_ctx);
git_SHA1_Init(&new_sha1_ctx);
if (lseek(pack_fd, 0, SEEK_SET) != 0)
die_errno("Failed seeking to start of '%s'", pack_name);
- if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
+ read_result = read_in_full(pack_fd, &hdr, sizeof(hdr));
+ if (read_result < 0)
die_errno("Unable to reread header of '%s'", pack_name);
+ else if (read_result != sizeof(hdr))
+ die_errno("Unexpected short read for header of '%s'",
+ pack_name);
if (lseek(pack_fd, 0, SEEK_SET) != 0)
die_errno("Failed seeking to start of '%s'", pack_name);
git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
diff --git a/sha1_file.c b/sha1_file.c
index 5a2014811f..09ad64ce55 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -1748,10 +1748,15 @@ static int index_core(unsigned char *sha1, int fd, size_t size,
ret = index_mem(sha1, "", size, type, path, flags);
} else if (size <= SMALL_FILE_SIZE) {
char *buf = xmalloc(size);
- if (size == read_in_full(fd, buf, size))
- ret = index_mem(sha1, buf, size, type, path, flags);
+ ssize_t read_result = read_in_full(fd, buf, size);
+ if (read_result < 0)
+ ret = error_errno("read error while indexing %s",
+ path ? path : "<unknown>");
+ else if (read_result != size)
+ ret = error("short read while indexing %s",
+ path ? path : "<unknown>");
else
- ret = error_errno("short read");
+ ret = index_mem(sha1, buf, size, type, path, flags);
free(buf);
} else {
void *buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
--
2.14.2.988.g01c8b37dde
next prev parent reply other threads:[~2017-09-27 6:01 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-25 20:26 [PATCH 0/7] read/write_in_full leftovers Jeff King
2017-09-25 20:27 ` [PATCH 1/7] files-backend: prefer "0" for write_in_full() error check Jeff King
2017-09-25 21:59 ` Jonathan Nieder
2017-09-25 23:13 ` Jeff King
2017-09-25 20:27 ` [PATCH 2/7] notes-merge: drop dead zero-write code Jeff King
2017-09-25 21:59 ` Jonathan Nieder
2017-09-25 20:29 ` [PATCH 3/7] read_in_full: reset errno before reading Jeff King
2017-09-25 22:09 ` Jonathan Nieder
2017-09-25 23:23 ` Jeff King
2017-09-25 23:33 ` Jonathan Nieder
2017-09-25 23:37 ` Jeff King
2017-09-25 23:45 ` Jeff King
2017-09-25 23:55 ` Jonathan Nieder
2017-09-26 0:01 ` Jeff King
2017-09-26 0:06 ` Stefan Beller
2017-09-26 0:09 ` Jeff King
2017-09-26 0:16 ` Jonathan Nieder
2017-09-26 0:17 ` Jonathan Nieder
2017-09-26 0:19 ` Jeff King
2017-09-26 0:22 ` Jonathan Nieder
2017-09-26 4:11 ` Junio C Hamano
2017-09-27 4:07 ` Jeff King
2017-09-27 4:27 ` Junio C Hamano
2017-09-26 0:13 ` Jonathan Nieder
2017-09-26 0:17 ` Jeff King
2017-09-26 0:20 ` Jonathan Nieder
2017-09-26 0:25 ` Jeff King
2017-09-26 0:28 ` Jonathan Nieder
2017-09-25 23:52 ` Jonathan Nieder
2017-09-25 20:29 ` [PATCH 4/7] get-tar-commit-id: prefer "!=" for read_in_full() error check Jeff King
2017-09-25 22:10 ` Jonathan Nieder
2017-09-25 20:30 ` [PATCH 5/7] worktree: use xsize_t to access file size Jeff King
2017-09-25 22:11 ` Jonathan Nieder
2017-09-25 20:31 ` [PATCH 6/7] worktree: check the result of read_in_full() Jeff King
2017-09-25 22:14 ` Jonathan Nieder
2017-09-25 23:25 ` Jeff King
2017-09-25 20:33 ` [PATCH 7/7] add xread_in_full() helper Jeff King
2017-09-25 22:16 ` Jonathan Nieder
2017-09-25 23:27 ` Jeff King
2017-09-27 5:54 ` [PATCH v2 0/7] read/write_in_full leftovers Jeff King
2017-09-27 6:00 ` [PATCH v2 1/7] files-backend: prefer "0" for write_in_full() error check Jeff King
2017-09-27 6:00 ` [PATCH v2 2/7] notes-merge: drop dead zero-write code Jeff King
2017-09-27 6:00 ` [PATCH v2 3/7] prefer "!=" when checking read_in_full() result Jeff King
2017-09-27 6:59 ` Junio C Hamano
2017-09-27 7:09 ` Jeff King
2017-09-27 6:01 ` Jeff King [this message]
2017-09-27 6:59 ` [PATCH v2 4/7] avoid looking at errno for short read_in_full() returns Junio C Hamano
2017-09-27 6:02 ` [PATCH v2 5/7] distinguish error versus short read from read_in_full() Jeff King
2017-09-27 6:02 ` [PATCH v2 6/7] worktree: use xsize_t to access file size Jeff King
2017-09-27 6:02 ` [PATCH v2 7/7] worktree: check the result of read_in_full() Jeff King
2017-09-27 6:57 ` [PATCH v2 0/7] read/write_in_full leftovers Junio C Hamano
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