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libsemanage: fsync final files before rename
Prior to rename(2)'ing the final selinux policy files into place,
fsync(2) them to ensure the contents will be fully written prior to
rename.  While we are here, also fix checking of write(2) to detect
short writes and treat them as an error.  This code could be more
generally improved but keeping to the minimal changes required to fix
this bug.

Fixes: SELinuxProject/selinux#237
Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Acked-by: Nicolas Iooss <nicolas.iooss@m4x.org>
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stephensmalley authored and bachradsusi committed May 15, 2020
1 parent 4159890 commit 331a109
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Showing 3 changed files with 23 additions and 11 deletions.
10 changes: 5 additions & 5 deletions libsemanage/src/direct_api.c
Expand Up @@ -1188,7 +1188,7 @@ static int semanage_compile_hll_modules(semanage_handle_t *sh,
* overwrite it. If source doesn't exist then return success.
* Returns 0 on success, -1 on error. */
static int copy_file_if_exists(const char *src, const char *dst, mode_t mode){
int rc = semanage_copy_file(src, dst, mode);
int rc = semanage_copy_file(src, dst, mode, false);
return (rc < 0 && errno != ENOENT) ? rc : 0;
}

Expand Down Expand Up @@ -1488,7 +1488,7 @@ static int semanage_direct_commit(semanage_handle_t * sh)
retval = semanage_copy_file(path,
semanage_path(SEMANAGE_TMP,
SEMANAGE_STORE_SEUSERS),
0);
0, false);
if (retval < 0)
goto cleanup;
pseusers->dtable->drop_cache(pseusers->dbase);
Expand All @@ -1506,7 +1506,7 @@ static int semanage_direct_commit(semanage_handle_t * sh)
retval = semanage_copy_file(path,
semanage_path(SEMANAGE_TMP,
SEMANAGE_USERS_EXTRA),
0);
0, false);
if (retval < 0)
goto cleanup;
pusers_extra->dtable->drop_cache(pusers_extra->dbase);
Expand Down Expand Up @@ -1595,7 +1595,7 @@ static int semanage_direct_commit(semanage_handle_t * sh)

retval = semanage_copy_file(semanage_path(SEMANAGE_TMP, SEMANAGE_STORE_KERNEL),
semanage_final_path(SEMANAGE_FINAL_TMP, SEMANAGE_KERNEL),
sh->conf->file_mode);
sh->conf->file_mode, false);
if (retval < 0) {
goto cleanup;
}
Expand Down Expand Up @@ -1634,7 +1634,7 @@ static int semanage_direct_commit(semanage_handle_t * sh)
retval = semanage_copy_file(
semanage_path(SEMANAGE_TMP, SEMANAGE_STORE_FC_HOMEDIRS),
semanage_final_path(SEMANAGE_FINAL_TMP, SEMANAGE_FC_HOMEDIRS),
sh->conf->file_mode);
sh->conf->file_mode, false);
if (retval < 0) {
goto cleanup;
}
Expand Down
20 changes: 15 additions & 5 deletions libsemanage/src/semanage_store.c
Expand Up @@ -707,7 +707,8 @@ static int semanage_filename_select(const struct dirent *d)

/* Copies a file from src to dst. If dst already exists then
* overwrite it. Returns 0 on success, -1 on error. */
int semanage_copy_file(const char *src, const char *dst, mode_t mode)
int semanage_copy_file(const char *src, const char *dst, mode_t mode,
bool syncrequired)
{
int in, out, retval = 0, amount_read, n, errsv = errno;
char tmp[PATH_MAX];
Expand Down Expand Up @@ -735,8 +736,11 @@ int semanage_copy_file(const char *src, const char *dst, mode_t mode)
}
umask(mask);
while (retval == 0 && (amount_read = read(in, buf, sizeof(buf))) > 0) {
if (write(out, buf, amount_read) < 0) {
errsv = errno;
if (write(out, buf, amount_read) != amount_read) {
if (errno)
errsv = errno;
else
errsv = EIO;
retval = -1;
}
}
Expand All @@ -745,6 +749,10 @@ int semanage_copy_file(const char *src, const char *dst, mode_t mode)
retval = -1;
}
close(in);
if (syncrequired && fsync(out) < 0) {
errsv = errno;
retval = -1;
}
if (close(out) < 0) {
errsv = errno;
retval = -1;
Expand Down Expand Up @@ -811,7 +819,8 @@ static int semanage_copy_dir_flags(const char *src, const char *dst, int flag)
umask(mask);
} else if (S_ISREG(sb.st_mode) && flag == 1) {
mask = umask(0077);
if (semanage_copy_file(path, path2, sb.st_mode) < 0) {
if (semanage_copy_file(path, path2, sb.st_mode,
false) < 0) {
umask(mask);
goto cleanup;
}
Expand Down Expand Up @@ -1639,7 +1648,8 @@ static int semanage_install_final_tmp(semanage_handle_t * sh)
goto cleanup;
}

ret = semanage_copy_file(src, dst, sh->conf->file_mode);
ret = semanage_copy_file(src, dst, sh->conf->file_mode,
true);
if (ret < 0) {
ERR(sh, "Could not copy %s to %s.", src, dst);
goto cleanup;
Expand Down
4 changes: 3 additions & 1 deletion libsemanage/src/semanage_store.h
Expand Up @@ -24,6 +24,7 @@
#ifndef SEMANAGE_MODULE_STORE_H
#define SEMANAGE_MODULE_STORE_H

#include <stdbool.h>
#include <sys/time.h>
#include <sepol/module.h>
#include <sepol/cil/cil.h>
Expand Down Expand Up @@ -162,6 +163,7 @@ int semanage_nc_sort(semanage_handle_t * sh,
size_t buf_len,
char **sorted_buf, size_t * sorted_buf_len);

int semanage_copy_file(const char *src, const char *dst, mode_t mode);
int semanage_copy_file(const char *src, const char *dst, mode_t mode,
bool syncrequired);

#endif

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