From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Date: Wed, 15 Nov 2006 16:27:54 +0000 (+0100)
Subject: Seek back to current filepos when mmap()ing with NO_MMAP
X-Git-Tag: v1.4.4.1~23
X-Git-Url: https://git.tokkee.org/?a=commitdiff_plain;h=0a3881d4cfee5c4ee3991a1b14a10333355958f1;p=git.git

Seek back to current filepos when mmap()ing with NO_MMAP

"git-index-pack --fix-thin" relies on mmap() not changing the current
file position (otherwise the pack will be corrupted when writing the
final SHA1). Meet that expectation.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
---

diff --git a/compat/mmap.c b/compat/mmap.c
index 55cb12076..a4d2e507f 100644
--- a/compat/mmap.c
+++ b/compat/mmap.c
@@ -7,6 +7,7 @@
 void *gitfakemmap(void *start, size_t length, int prot , int flags, int fd, off_t offset)
 {
 	int n = 0;
+	off_t current_offset = lseek(fd, 0, SEEK_CUR);
 
 	if (start != NULL || !(flags & MAP_PRIVATE))
 		die("Invalid usage of gitfakemmap.");
@@ -39,6 +40,11 @@ void *gitfakemmap(void *start, size_t length, int prot , int flags, int fd, off_
 		n += count;
 	}
 
+	if (current_offset != lseek(fd, current_offset, SEEK_SET)) {
+		errno = EINVAL;
+		return MAP_FAILED;
+	}
+
 	return start;
 }