]> git.ipfire.org Git - thirdparty/git.git/blame - update-ref.c
fix potential deadlock in create_one_file
[thirdparty/git.git] / update-ref.c
CommitLineData
66bf85a4
LT
1#include "cache.h"
2#include "refs.h"
3
4static const char git_update_ref_usage[] = "git-update-ref <refname> <value> [<oldval>]";
5
152da3df
JH
6static int re_verify(const char *path, unsigned char *oldsha1, unsigned char *currsha1)
7{
8 char buf[40];
9 int fd = open(path, O_RDONLY), nr;
10 if (fd < 0)
11 return -1;
12 nr = read(fd, buf, 40);
13 close(fd);
14 if (nr != 40 || get_sha1_hex(buf, currsha1) < 0)
15 return -1;
16 return memcmp(oldsha1, currsha1, 20) ? -1 : 0;
17}
18
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LT
19int main(int argc, char **argv)
20{
21 char *hex;
08db81a9
AR
22 const char *refname, *value, *oldval, *path;
23 char *lockpath;
66bf85a4
LT
24 unsigned char sha1[20], oldsha1[20], currsha1[20];
25 int fd, written;
26
27 setup_git_directory();
28 if (argc < 3 || argc > 4)
29 usage(git_update_ref_usage);
30
31 refname = argv[1];
32 value = argv[2];
33 oldval = argv[3];
34 if (get_sha1(value, sha1) < 0)
35 die("%s: not a valid SHA1", value);
36 memset(oldsha1, 0, 20);
37 if (oldval && get_sha1(oldval, oldsha1) < 0)
38 die("%s: not a valid old SHA1", oldval);
39
a876ed83 40 path = resolve_ref(git_path("%s", refname), currsha1, !!oldval);
66bf85a4
LT
41 if (!path)
42 die("No such ref: %s", refname);
43
44 if (oldval) {
45 if (memcmp(currsha1, oldsha1, 20))
ad7db621 46 die("Ref %s is at %s but expected %s", refname, sha1_to_hex(currsha1), sha1_to_hex(oldsha1));
66bf85a4
LT
47 /* Nothing to do? */
48 if (!memcmp(oldsha1, sha1, 20))
49 exit(0);
50 }
51 path = strdup(path);
52 lockpath = mkpath("%s.lock", path);
08db81a9
AR
53 if (safe_create_leading_directories(lockpath) < 0)
54 die("Unable to create all of %s", lockpath);
66bf85a4
LT
55
56 fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
57 if (fd < 0)
58 die("Unable to create %s", lockpath);
59 hex = sha1_to_hex(sha1);
60 hex[40] = '\n';
61 written = write(fd, hex, 41);
62 close(fd);
63 if (written != 41) {
64 unlink(lockpath);
65 die("Unable to write to %s", lockpath);
66 }
67
68 /*
152da3df 69 * Re-read the ref after getting the lock to verify
66bf85a4 70 */
152da3df
JH
71 if (oldval && re_verify(path, oldsha1, currsha1) < 0) {
72 unlink(lockpath);
73 die("Ref lock failed");
74 }
66bf85a4 75
152da3df
JH
76 /*
77 * Finally, replace the old ref with the new one
78 */
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LT
79 if (rename(lockpath, path) < 0) {
80 unlink(lockpath);
81 die("Unable to create %s", path);
82 }
83 return 0;
84}