File depmod-Prevent-module-dependency-files-corrupti... of Package kmod

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File depmod-Prevent-module-dependency-files-corruption-du.patch of Package kmod

From ad2e531f57cf08bc33469c5baab5de6faf359acf Mon Sep 17 00:00:00 2001
From: Michal Suchanek <msuchanek@suse.de>
Date: Mon, 17 Dec 2018 23:46:28 +0100
Subject: [PATCH] depmod: prevent module dependency files corruption due to
 parallel invocation.

Depmod does not use unique filename for temporary files. There is no
guarantee the user does not attempt to run mutiple depmod processes in
parallel. If that happens a temporary file might be created by
depmod(1st), truncated by depmod(2nd), and renamed to final name by
depmod(1st) resulting in corrupted file seen by user.

Due to missing mkstempat() this is more complex than it should be.
Adding PID and timestamp to the filename should be reasonably reliable.
Adding O_EXCL as mkstemp does fails creating the file rather than
corrupting existing file.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
 tools/depmod.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/depmod.c b/tools/depmod.c
index 40ec74693323..9f3712f4d37a 100644
--- a/tools/depmod.c
+++ b/tools/depmod.c
@@ -28,6 +28,7 @@
 #include <string.h>
 #include <limits.h>
 #include <dirent.h>
+#include <sys/time.h>
 #include <sys/utsname.h>
 #include <sys/stat.h>
 #include <regex.h>
@@ -2144,6 +2145,9 @@ static int depmod_output(struct depmod *depmod, FILE *out)
 	};
 	const char *dname = depmod->cfg->dirname;
 	int dfd, err = 0;
+	struct timeval tv;
+
+	gettimeofday(&tv, NULL);
 
 	if (out != NULL)
 		dfd = -1;
@@ -2162,11 +2166,12 @@ static int depmod_output(struct depmod *depmod, FILE *out)
 		int r, ferr;
 
 		if (fp == NULL) {
-			int flags = O_CREAT | O_TRUNC | O_WRONLY;
+			int flags = O_CREAT | O_EXCL | O_WRONLY;
 			int mode = 0644;
 			int fd;
 
-			snprintf(tmp, sizeof(tmp), "%s.tmp", itr->name);
+			snprintf(tmp, sizeof(tmp), "%s.%i.%li.%li", itr->name, getpid(),
+					tv.tv_usec, tv.tv_sec);
 			fd = openat(dfd, tmp, flags, mode);
 			if (fd < 0) {
 				ERR("openat(%s, %s, %o, %o): %m\n",
-- 
2.19.2

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File depmod-Prevent-module-dependency-files-corruption-du.patch of Package kmod

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