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authorGiuseppe Scrivano <gscrivan@redhat.com>2019-12-04 10:25:54 +0100
committerGiuseppe Scrivano <gscrivan@redhat.com>2019-12-04 10:30:40 +0100
commita94e625868c4188dfd3a522f2b24ff9ca3905b64 (patch)
treed9ee3411747bfc12239b3799f1cdf05775e92087
parent5c3af009c6027429d60f6e73bf3ade346ec3d410 (diff)
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rootless: add fallback for renameat2 at runtime
the renameat2 syscall might be defined in the C library but lacking support in the kernel. In such case, let it fallback to open(O_CREAT)+rename as it does on systems lacking the definition for renameat2. Closes: https://github.com/containers/libpod/issues/4570 Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
-rw-r--r--pkg/rootless/rootless_linux.c33
1 files changed, 20 insertions, 13 deletions
diff --git a/pkg/rootless/rootless_linux.c b/pkg/rootless/rootless_linux.c
index 9604de638..193c788c0 100644
--- a/pkg/rootless/rootless_linux.c
+++ b/pkg/rootless/rootless_linux.c
@@ -19,24 +19,31 @@
#include <sys/select.h>
#include <stdio.h>
-#ifndef RENAME_NOREPLACE
-# define RENAME_NOREPLACE (1 << 0)
-
-int renameat2 (int olddirfd, const char *oldpath, int newdirfd, const char *newpath, unsigned int flags)
+int rename_noreplace (int olddirfd, const char *oldpath, int newdirfd, const char *newpath)
{
+ int ret;
+
# ifdef SYS_renameat2
- return (int) syscall (SYS_renameat2, olddirfd, oldpath, newdirfd, newpath, flags);
-# else
+# ifndef RENAME_NOREPLACE
+# define RENAME_NOREPLACE (1 << 0)
+# endif
+
+ ret = (int) syscall (SYS_renameat2, olddirfd, oldpath, newdirfd, newpath, RENAME_NOREPLACE);
+ if (ret == 0 || errno != EINVAL)
+ return ret;
+
+ /* Fallback in case of errno==EINVAL. */
+# endif
+
/* This might be an issue if another process is trying to read the file while it is empty. */
- int fd = open (newpath, O_EXCL|O_CREAT, 0700);
- if (fd < 0)
- return fd;
- close (fd);
+ ret = open (newpath, O_EXCL|O_CREAT, 0700);
+ if (ret < 0)
+ return ret;
+ close (ret);
+
/* We are sure we created the file, let's overwrite it. */
return rename (oldpath, newpath);
-# endif
}
-#endif
#ifndef TEMP_FAILURE_RETRY
#define TEMP_FAILURE_RETRY(expression) \
@@ -453,7 +460,7 @@ create_pause_process (const char *pause_pid_file_path, char **argv)
/* There can be another process at this point trying to configure the user namespace and the pause
process, do not override the pid file if it already exists. */
- if (renameat2 (AT_FDCWD, tmp_file_path, AT_FDCWD, pause_pid_file_path, RENAME_NOREPLACE) < 0)
+ if (rename_noreplace (AT_FDCWD, tmp_file_path, AT_FDCWD, pause_pid_file_path) < 0)
{
unlink (tmp_file_path);
kill (pid, SIGKILL);