From eb3da9012f462da2451edeb8d67c5b67c833a0b1 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Fri, 13 Nov 2015 00:54:56 +0100 Subject: [PATCH] util-lib: optionally, when writing a string to a file, verify string on failure With this change, the idiom: r = write_string_file(p, buf, 0); if (r < 0) { if (verify_one_line_file(p, buf) > 0) r = 0; } gets reduced to: r = write_string_file(p, buf, WRITE_STRING_FILE_VERIFY_ON_FAILURE); i.e. when writing the string fails and the new flag WRITE_STRING_FILE_VERIFY_ON_FAILURE is specified we'll not return a failure immediately, but check the contents of the file. If it matches what we wanted to write we suppress the error and exit cleanly. --- src/basic/fileio.c | 83 +++++++++++++++++++++++++++++++++++++-------- src/basic/fileio.h | 3 +- src/network/networkd-link.c | 54 +++++++---------------------- src/test/test-fileio.c | 21 ++++++++++++ 4 files changed, 104 insertions(+), 57 deletions(-) diff --git a/src/basic/fileio.c b/src/basic/fileio.c index be6e327..10aacdc 100644 --- a/src/basic/fileio.c +++ b/src/basic/fileio.c @@ -78,6 +78,7 @@ static int write_string_file_atomic(const char *fn, const char *line, bool enfor int write_string_file(const char *fn, const char *line, WriteStringFileFlags flags) { _cleanup_fclose_ FILE *f = NULL; + int q, r; assert(fn); assert(line); @@ -85,30 +86,58 @@ int write_string_file(const char *fn, const char *line, WriteStringFileFlags fla if (flags & WRITE_STRING_FILE_ATOMIC) { assert(flags & WRITE_STRING_FILE_CREATE); - return write_string_file_atomic(fn, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE)); + r = write_string_file_atomic(fn, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE)); + if (r < 0) + goto fail; + + return r; } if (flags & WRITE_STRING_FILE_CREATE) { f = fopen(fn, "we"); - if (!f) - return -errno; + if (!f) { + r = -errno; + goto fail; + } } else { int fd; /* We manually build our own version of fopen(..., "we") that * works without O_CREAT */ fd = open(fn, O_WRONLY|O_CLOEXEC|O_NOCTTY); - if (fd < 0) - return -errno; + if (fd < 0) { + r = -errno; + goto fail; + } f = fdopen(fd, "we"); if (!f) { + r = -errno; safe_close(fd); - return -errno; + goto fail; } } - return write_string_stream(f, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE)); + r = write_string_stream(f, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE)); + if (r < 0) + goto fail; + + return 0; + +fail: + if (!(flags & WRITE_STRING_FILE_VERIFY_ON_FAILURE)) + return r; + + f = safe_fclose(f); + + /* OK, the operation failed, but let's see if the right + * contents in place already. If so, eat up the error. */ + + q = verify_file(fn, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE)); + if (q <= 0) + return r; + + return 0; } int read_one_line_file(const char *fn, char **line) { @@ -139,15 +168,41 @@ int read_one_line_file(const char *fn, char **line) { return 0; } -int verify_one_line_file(const char *fn, const char *line) { - _cleanup_free_ char *value = NULL; - int r; +int verify_file(const char *fn, const char *blob, bool accept_extra_nl) { + _cleanup_fclose_ FILE *f = NULL; + _cleanup_free_ char *buf = NULL; + size_t l, k; - r = read_one_line_file(fn, &value); - if (r < 0) - return r; + assert(fn); + assert(blob); + + l = strlen(blob); + + if (accept_extra_nl && endswith(blob, "\n")) + accept_extra_nl = false; + + buf = malloc(l + accept_extra_nl + 1); + if (!buf) + return -ENOMEM; - return streq(value, line); + f = fopen(fn, "re"); + if (!f) + return -errno; + + /* We try to read one byte more than we need, so that we know whether we hit eof */ + errno = 0; + k = fread(buf, 1, l + accept_extra_nl + 1, f); + if (ferror(f)) + return errno > 0 ? -errno : -EIO; + + if (k != l && k != l + accept_extra_nl) + return 0; + if (memcmp(buf, blob, l) != 0) + return 0; + if (k > l && buf[l] != '\n') + return 0; + + return 1; } int read_full_stream(FILE *f, char **contents, size_t *size) { diff --git a/src/basic/fileio.h b/src/basic/fileio.h index 5f2c941..95e8698 100644 --- a/src/basic/fileio.h +++ b/src/basic/fileio.h @@ -34,6 +34,7 @@ typedef enum { WRITE_STRING_FILE_CREATE = 1, WRITE_STRING_FILE_ATOMIC = 2, WRITE_STRING_FILE_AVOID_NEWLINE = 4, + WRITE_STRING_FILE_VERIFY_ON_FAILURE = 8, } WriteStringFileFlags; int write_string_stream(FILE *f, const char *line, bool enforce_newline); @@ -43,7 +44,7 @@ int read_one_line_file(const char *fn, char **line); int read_full_file(const char *fn, char **contents, size_t *size); int read_full_stream(FILE *f, char **contents, size_t *size); -int verify_one_line_file(const char *fn, const char *line); +int verify_file(const char *fn, const char *blob, bool accept_extra_nl); int parse_env_file(const char *fname, const char *separator, ...) _sentinel_; int load_env_file(FILE *f, const char *fname, const char *separator, char ***l); diff --git a/src/network/networkd-link.c b/src/network/networkd-link.c index 00c57b2..07910c2 100644 --- a/src/network/networkd-link.c +++ b/src/network/networkd-link.c @@ -1859,14 +1859,9 @@ static int link_set_ipv4_forward(Link *link) { p = strjoina("/proc/sys/net/ipv4/conf/", link->ifname, "/forwarding"); v = one_zero(link_ipv4_forward_enabled(link)); - r = write_string_file(p, v, 0); - if (r < 0) { - /* If the right value is set anyway, don't complain */ - if (verify_one_line_file(p, v) > 0) - return 0; - + r = write_string_file(p, v, WRITE_STRING_FILE_VERIFY_ON_FAILURE); + if (r < 0) log_link_warning_errno(link, r, "Cannot configure IPv4 forwarding for interface %s: %m", link->ifname); - } return 0; } @@ -1888,14 +1883,9 @@ static int link_set_ipv6_forward(Link *link) { p = strjoina("/proc/sys/net/ipv6/conf/", link->ifname, "/forwarding"); v = one_zero(link_ipv6_forward_enabled(link)); - r = write_string_file(p, v, 0); - if (r < 0) { - /* If the right value is set anyway, don't complain */ - if (verify_one_line_file(p, v) > 0) - return 0; - + r = write_string_file(p, v, WRITE_STRING_FILE_VERIFY_ON_FAILURE); + if (r < 0) log_link_warning_errno(link, r, "Cannot configure IPv6 forwarding for interface: %m"); - } return 0; } @@ -1917,14 +1907,9 @@ static int link_set_ipv6_privacy_extensions(Link *link) { p = strjoina("/proc/sys/net/ipv6/conf/", link->ifname, "/use_tempaddr"); xsprintf(buf, "%u", link->network->ipv6_privacy_extensions); - r = write_string_file(p, buf, 0); - if (r < 0) { - /* If the right value is set anyway, don't complain */ - if (verify_one_line_file(p, buf) > 0) - return 0; - + r = write_string_file(p, buf, WRITE_STRING_FILE_VERIFY_ON_FAILURE); + if (r < 0) log_link_warning_errno(link, r, "Cannot configure IPv6 privacy extension for interface: %m"); - } return 0; } @@ -1943,14 +1928,9 @@ static int link_set_ipv6_accept_ra(Link *link) { p = strjoina("/proc/sys/net/ipv6/conf/", link->ifname, "/accept_ra"); /* we handle router advertisments ourselves, tell the kernel to GTFO */ - r = write_string_file(p, "0", 0); - if (r < 0) { - /* If the right value is set anyway, don't complain */ - if (verify_one_line_file(p, "0") > 0) - return 0; - + r = write_string_file(p, "0", WRITE_STRING_FILE_VERIFY_ON_FAILURE); + if (r < 0) log_link_warning_errno(link, r, "Cannot disable kernel IPv6 accept_ra for interface: %m"); - } return 0; } @@ -1974,14 +1954,9 @@ static int link_set_ipv6_dad_transmits(Link *link) { xsprintf(buf, "%u", link->network->ipv6_dad_transmits); - r = write_string_file(p, buf, 0); - if (r < 0) { - /* If the right value is set anyway, don't complain */ - if (verify_one_line_file(p, buf) > 0) - return 0; - + r = write_string_file(p, buf, WRITE_STRING_FILE_VERIFY_ON_FAILURE); + if (r < 0) log_link_warning_errno(link, r, "Cannot set IPv6 dad transmits for interface: %m"); - } return 0; } @@ -2005,14 +1980,9 @@ static int link_set_ipv6_hop_limit(Link *link) { xsprintf(buf, "%u", link->network->ipv6_hop_limit); - r = write_string_file(p, buf, 0); - if (r < 0) { - /* If the right value is set anyway, don't complain */ - if (verify_one_line_file(p, buf) > 0) - return 0; - + r = write_string_file(p, buf, WRITE_STRING_FILE_VERIFY_ON_FAILURE); + if (r < 0) log_link_warning_errno(link, r, "Cannot set IPv6 hop limit for interface: %m"); - } return 0; } diff --git a/src/test/test-fileio.c b/src/test/test-fileio.c index e588681..bde3c7c 100644 --- a/src/test/test-fileio.c +++ b/src/test/test-fileio.c @@ -363,6 +363,26 @@ static void test_write_string_file_no_create(void) { unlink(fn); } +static void test_write_string_file_verify(void) { + _cleanup_free_ char *buf = NULL, *buf2 = NULL; + int r; + + assert_se(read_one_line_file("/proc/cmdline", &buf) >= 0); + assert_se((buf2 = strjoin(buf, "\n", NULL))); + + r = write_string_file("/proc/cmdline", buf, 0); + assert_se(r == -EACCES || r == -EIO); + r = write_string_file("/proc/cmdline", buf2, 0); + assert_se(r == -EACCES || r == -EIO); + + assert_se(write_string_file("/proc/cmdline", buf, WRITE_STRING_FILE_VERIFY_ON_FAILURE) == 0); + assert_se(write_string_file("/proc/cmdline", buf2, WRITE_STRING_FILE_VERIFY_ON_FAILURE) == 0); + + r = write_string_file("/proc/cmdline", buf, WRITE_STRING_FILE_VERIFY_ON_FAILURE|WRITE_STRING_FILE_AVOID_NEWLINE); + assert_se(r == -EACCES || r == -EIO); + assert_se(write_string_file("/proc/cmdline", buf2, WRITE_STRING_FILE_VERIFY_ON_FAILURE|WRITE_STRING_FILE_AVOID_NEWLINE) == 0); +} + static void test_load_env_file_pairs(void) { char fn[] = "/tmp/test-load_env_file_pairs-XXXXXX"; int fd; @@ -419,6 +439,7 @@ int main(int argc, char *argv[]) { test_write_string_stream(); test_write_string_file(); test_write_string_file_no_create(); + test_write_string_file_verify(); test_load_env_file_pairs(); return 0; -- 2.7.4