From a07f46a3b0f7e452d50690b831bb4c99fbc6650f Mon Sep 17 00:00:00 2001 From: Joel Rosdahl Date: Sat, 8 Nov 2014 16:53:34 +0100 Subject: [PATCH] Do not rely on pids being unique Based on a patch by Mike Frysinger : "Linux supports creating pid namespaces cheaply and running processes inside of them. When you try to share a single cache among multiple such runs, the fact that the code relies on pid numbers as globally unique values quickly fails. Instead, switch to standard mkstemp to generate temp files for us." --- ccache.c | 22 ++++++++++++++-------- ccache.h | 2 +- manifest.c | 2 +- stats.c | 10 ++++++++-- util.c | 18 +++++++++++------- 5 files changed, 35 insertions(+), 19 deletions(-) diff --git a/ccache.c b/ccache.c index f0dca22c7..7b9fd0b04 100644 --- a/ccache.c +++ b/ccache.c @@ -613,8 +613,11 @@ to_cache(struct args *args) unsigned added_files = 0; tmp_stdout = format("%s.tmp.stdout.%s", cached_obj, tmp_string()); + create_empty_file(tmp_stdout); tmp_stderr = format("%s.tmp.stderr.%s", cached_obj, tmp_string()); + create_empty_file(tmp_stderr); tmp_obj = format("%s.tmp.%s", cached_obj, tmp_string()); + create_empty_file(tmp_obj); args_add(args, "-o"); args_add(args, tmp_obj); @@ -666,7 +669,7 @@ to_cache(struct args *args) int fd_result; char *tmp_stderr2; - tmp_stderr2 = format("%s.tmp.stderr2.%s", cached_obj, tmp_string()); + tmp_stderr2 = format("%s.2", tmp_stderr); if (x_rename(tmp_stderr, tmp_stderr2)) { cc_log("Failed to rename %s to %s: %s", tmp_stderr, tmp_stderr2, strerror(errno)); @@ -808,13 +811,21 @@ get_object_name_from_cpp(struct args *args, struct mdfour *hash) } path_stderr = format("%s/tmp.cpp_stderr.%s", temp_dir, tmp_string()); + create_empty_file(path_stderr); add_pending_tmp_file(path_stderr); time_of_compilation = time(NULL); if (!direct_i_file) { - path_stdout = format("%s/%s.tmp.%s.%s", - temp_dir, input_base, tmp_string(), i_extension); + /* The temporary file needs the proper i_extension for the compiler to do + * its thing. However, create_empty_file requires the tmp_string() part to + * be last, which is why the temporary file is created in two steps. */ + char *path_stdout_tmp = + format("%s/%s.tmp.%s", temp_dir, input_base, tmp_string()); + create_empty_file(path_stdout_tmp); + path_stdout = format("%s.%s", path_stdout_tmp, i_extension); + x_rename(path_stdout_tmp, path_stdout); + free(path_stdout_tmp); add_pending_tmp_file(path_stdout); /* run cpp on the input file to obtain the .i */ @@ -827,11 +838,6 @@ get_object_name_from_cpp(struct args *args, struct mdfour *hash) can skip the cpp stage and directly form the correct i_tmpfile */ path_stdout = input_file; - if (create_empty_file(path_stderr) != 0) { - cc_log("Failed to create %s: %s", path_stderr, strerror(errno)); - stats_update(STATS_ERROR); - failed(); - } status = 0; } diff --git a/ccache.h b/ccache.h index ce4d1cf57..adcc38160 100644 --- a/ccache.h +++ b/ccache.h @@ -133,7 +133,7 @@ size_t file_size(struct stat *st); int safe_open(const char *fname); char *x_realpath(const char *path); char *gnu_getcwd(void); -int create_empty_file(const char *fname); +int create_empty_file(char *fname); const char *get_home_directory(void); char *get_cwd(); bool same_executable_name(const char *s1, const char *s2); diff --git a/manifest.c b/manifest.c index 7977418b0..660d437f6 100644 --- a/manifest.c +++ b/manifest.c @@ -653,7 +653,7 @@ manifest_put(const char *manifest_path, struct file_hash *object_hash, } tmp_file = format("%s.tmp.%s", manifest_path, tmp_string()); - fd2 = safe_open(tmp_file); + fd2 = mkstemp(tmp_file); if (fd2 == -1) { cc_log("Failed to open %s", tmp_file); goto out; diff --git a/stats.c b/stats.c index d7321265c..76cea8355 100644 --- a/stats.c +++ b/stats.c @@ -126,9 +126,15 @@ stats_write(const char *path, struct counters *counters) size_t i; char *tmp_file; FILE *f; + int fd; tmp_file = format("%s.tmp.%s", path, tmp_string()); - f = fopen(tmp_file, "wb"); + fd = mkstemp(tmp_file); + if (fd == -1) { + cc_log("Failed to open %s", tmp_file); + goto end; + } + f = fdopen(fd, "wb"); if (!f) { cc_log("Failed to open %s", tmp_file); goto end; @@ -138,7 +144,7 @@ stats_write(const char *path, struct counters *counters) fatal("Failed to write to %s", tmp_file); } } - fclose(f); + fclose(f); /* This also implicitly closes the fd. */ x_rename(tmp_file, path); end: diff --git a/util.c b/util.c index ed470d2c3..4c18e1576 100644 --- a/util.c +++ b/util.c @@ -195,7 +195,7 @@ copy_file(const char *src, const char *dest, int compress_dest) struct stat st; int errnum; - tmp_name = format("%s.%s.XXXXXX", dest, tmp_string()); + tmp_name = format("%s.%s", dest, tmp_string()); cc_log("Copying %s to %s via %s (%s)", src, dest, tmp_name, compress_dest ? "compressed": "uncompressed"); @@ -418,8 +418,8 @@ get_hostname(void) } /* - * Return a string to be used to distinguish temporary files. Also tries to - * cope with NFS by adding the local hostname. + * Return a string to be passed to mkstemp to create a temporary file. Also + * tries to cope with NFS by adding the local hostname. */ const char * tmp_string(void) @@ -427,7 +427,7 @@ tmp_string(void) static char *ret; if (!ret) { - ret = format("%s.%u", get_hostname(), (unsigned)getpid()); + ret = format("%s.%u.XXXXXX", get_hostname(), (unsigned)getpid()); } return ret; @@ -886,12 +886,13 @@ gnu_getcwd(void) /* create an empty file */ int -create_empty_file(const char *fname) +create_empty_file(char *fname) { int fd; - fd = open(fname, O_WRONLY|O_CREAT|O_TRUNC|O_EXCL|O_BINARY, 0666); + fd = mkstemp(fname); if (fd == -1) { + cc_log("Failed to create %s: %s", fname, strerror(errno)); return -1; } close(fd); @@ -1126,7 +1127,10 @@ x_unlink(const char *path) goto out; } if (unlink(tmp_name) == -1) { - result = -1; + /* If it was released in a race, that's OK. */ + if (errno != ENOENT) { + result = -1; + } } out: free(tmp_name); -- 2.47.2