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From a06bacf500d56b72b5f9b121ebf7f6af9e3df185 Mon Sep 17 00:00:00 2001
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From: Michal Suchanek <msuchanek@suse.de>
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Date: Mon, 17 Dec 2018 23:46:28 +0100
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Subject: [PATCH 2/2] depmod: prevent module dependency files corruption due to
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parallel invocation.
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Depmod does not use unique filename for temporary files. There is no
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guarantee the user does not attempt to run mutiple depmod processes in
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parallel. If that happens a temporary file might be created by
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depmod(1st), truncated by depmod(2nd), and renamed to final name by
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depmod(1st) resulting in corrupted file seen by user.
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Due to missing mkstempat() this is more complex than it should be.
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Adding PID and timestamp to the filename should be reasonably reliable.
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Adding O_EXCL as mkstemp does fails creating the file rather than
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corrupting existing file.
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Signed-off-by: Michal Suchanek <msuchanek@suse.de>
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---
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tools/depmod.c | 9 +++++++--
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1 file changed, 7 insertions(+), 2 deletions(-)
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diff --git a/tools/depmod.c b/tools/depmod.c
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index 18c0d61b2db3..0f7e33ccfd59 100644
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--- a/tools/depmod.c
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+++ b/tools/depmod.c
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@@ -29,6 +29,7 @@
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#include <string.h>
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#include <unistd.h>
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#include <sys/stat.h>
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+#include <sys/time.h>
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#include <sys/utsname.h>
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#include <shared/array.h>
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@@ -2398,6 +2399,9 @@ static int depmod_output(struct depmod *depmod, FILE *out)
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};
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const char *dname = depmod->cfg->dirname;
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int dfd, err = 0;
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+ struct timeval tv;
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+
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+ gettimeofday(&tv, NULL);
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if (out != NULL)
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dfd = -1;
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@@ -2416,11 +2420,12 @@ static int depmod_output(struct depmod *depmod, FILE *out)
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int r, ferr;
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if (fp == NULL) {
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- int flags = O_CREAT | O_TRUNC | O_WRONLY;
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+ int flags = O_CREAT | O_EXCL | O_WRONLY;
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int mode = 0644;
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int fd;
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- snprintf(tmp, sizeof(tmp), "%s.tmp", itr->name);
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+ snprintf(tmp, sizeof(tmp), "%s.%i.%li.%li", itr->name, getpid(),
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+ tv.tv_usec, tv.tv_sec);
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fd = openat(dfd, tmp, flags, mode);
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if (fd < 0) {
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ERR("openat(%s, %s, %o, %o): %m\n",
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--
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2.33.0
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