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Merge pull request #18472 from poettering/conservative-rename-fix

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fix conservative_renameat()
This commit is contained in:
Lennart Poettering 2021-02-04 22:08:47 +01:00 committed by GitHub
commit a24fb9b2ce
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2 changed files with 43 additions and 13 deletions
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28
src/basic/fs-util.c
View File

@ -1656,23 +1656,37 @@ int conservative_renameat(
goto do_rename;
for (;;) {
char buf1[16*1024];
char buf2[sizeof(buf1) + 1];
uint8_t buf1[16*1024];
uint8_t buf2[sizeof(buf1)];
ssize_t l1, l2;
l1 = read(old_fd, buf1, sizeof(buf1));
if (l1 < 0)
goto do_rename;
l2 = read(new_fd, buf2, l1 + 1);
if (l1 != l2)
goto do_rename;
if (l1 == sizeof(buf1))
/* Read the full block, hence read a full block in the other file too */
if (l1 == 0) /* EOF on both! And everything's the same so far, yay! */
break;
l2 = read(new_fd, buf2, l1);
else {
assert((size_t) l1 < sizeof(buf1));
/* Short read. This hence was the last block in the first file, and then came
* EOF. Read one byte more in the second file, so that we can verify we hit EOF there
* too. */
assert((size_t) (l1 + 1) <= sizeof(buf2));
l2 = read(new_fd, buf2, l1 + 1);
}
if (l2 != l1)
goto do_rename;
if (memcmp(buf1, buf2, l1) != 0)
goto do_rename;
if ((size_t) l1 < sizeof(buf1)) /* We hit EOF on the first file, and the second file too, hence exit
* now. */
break;
}
is_same:

28
src/test/test-fs-util.c
View File

@ -11,6 +11,7 @@
#include "macro.h"
#include "mkdir.h"
#include "path-util.h"
#include "random-util.h"
#include "rm-rf.h"
#include "stdio-util.h"
#include "string-util.h"
@ -836,12 +837,24 @@ static void test_path_is_encrypted(void) {
test_path_is_encrypted_one("/dev", booted > 0 ? false : -1);
}
static void create_binary_file(const char *p, const void *data, size_t l) {
_cleanup_close_ int fd = -1;
fd = open(p, O_CREAT|O_WRONLY|O_EXCL|O_CLOEXEC, 0600);
assert_se(fd >= 0);
assert_se(write(fd, data, l) == (ssize_t) l);
}
static void test_conservative_rename(void) {
_cleanup_(unlink_and_freep) char *p = NULL;
_cleanup_free_ char *q = NULL;
size_t l = 16*1024 + random_u64() % (32 * 1024); /* some randomly sized buffer 16k…48k */
uint8_t buffer[l+1];
random_bytes(buffer, l);
assert_se(tempfn_random_child(NULL, NULL, &p) >= 0);
assert_se(write_string_file(p, "this is a test", WRITE_STRING_FILE_CREATE) >= 0);
create_binary_file(p, buffer, l);
assert_se(tempfn_random_child(NULL, NULL, &q) >= 0);
@ -856,27 +869,30 @@ static void test_conservative_rename(void) {
assert_se(access(q, F_OK) < 0 && errno == ENOENT);
/* Check that a manual new writeout is also detected */
assert_se(write_string_file(q, "this is a test", WRITE_STRING_FILE_CREATE) >= 0);
create_binary_file(q, buffer, l);
assert_se(conservative_renameat(AT_FDCWD, q, AT_FDCWD, p) == 0);
assert_se(access(q, F_OK) < 0 && errno == ENOENT);
/* Check that a minimally changed version is detected */
assert_se(write_string_file(q, "this is a_test", WRITE_STRING_FILE_CREATE) >= 0);
buffer[47] = ~buffer[47];
create_binary_file(q, buffer, l);
assert_se(conservative_renameat(AT_FDCWD, q, AT_FDCWD, p) > 0);
assert_se(access(q, F_OK) < 0 && errno == ENOENT);
/* Check that this really is new updated version */
assert_se(write_string_file(q, "this is a_test", WRITE_STRING_FILE_CREATE) >= 0);
create_binary_file(q, buffer, l);
assert_se(conservative_renameat(AT_FDCWD, q, AT_FDCWD, p) == 0);
assert_se(access(q, F_OK) < 0 && errno == ENOENT);
/* Make sure we detect extended files */
assert_se(write_string_file(q, "this is a_testx", WRITE_STRING_FILE_CREATE) >= 0);
buffer[l++] = 47;
create_binary_file(q, buffer, l);
assert_se(conservative_renameat(AT_FDCWD, q, AT_FDCWD, p) > 0);
assert_se(access(q, F_OK) < 0 && errno == ENOENT);
/* Make sure we detect truncated files */
assert_se(write_string_file(q, "this is a_test", WRITE_STRING_FILE_CREATE) >= 0);
l--;
create_binary_file(q, buffer, l);
assert_se(conservative_renameat(AT_FDCWD, q, AT_FDCWD, p) > 0);
assert_se(access(q, F_OK) < 0 && errno == ENOENT);
}