commit: b55840ebe3278032777a3b52cecc6dac325dcf85 Author: Mike Gilbert <floppym <AT> gentoo <DOT> org> AuthorDate: Mon Jun 19 15:50:46 2023 +0000 Commit: Mike Gilbert <floppym <AT> gentoo <DOT> org> CommitDate: Wed Jun 21 14:40:08 2023 +0000 URL: https://gitweb.gentoo.org/proj/sandbox.git/commit/?id=b55840eb
libsbutil: add sb_exists function This provides a central place to work around a bug on musl where faccessat sets errno to EINVAL when the kernel does not support faccessat2. Bug: https://bugs.gentoo.org/908765 Signed-off-by: Mike Gilbert <floppym <AT> gentoo.org> libsandbox/pre_check_openat.c | 2 +- libsandbox/wrapper-funcs/fopen_pre_check.c | 2 +- libsbutil/local.mk | 1 + libsbutil/sb_exists.c | 24 ++++++++++++++++++++++++ libsbutil/sbutil.h | 1 + libsbutil/src/file.c | 2 +- 6 files changed, 29 insertions(+), 3 deletions(-) diff --git a/libsandbox/pre_check_openat.c b/libsandbox/pre_check_openat.c index 8fd3b23..99c03eb 100644 --- a/libsandbox/pre_check_openat.c +++ b/libsandbox/pre_check_openat.c @@ -19,7 +19,7 @@ bool sb_openat_pre_check(const char *func, const char *pathname, int dirfd, int save_errno(); /* Doesn't exist -> skip permission checks */ - if (faccessat(dirfd, pathname, F_OK, (flags & O_NOFOLLOW) ? AT_SYMLINK_NOFOLLOW : 0) == -1) { + if (sb_exists(dirfd, pathname, (flags & O_NOFOLLOW) ? AT_SYMLINK_NOFOLLOW : 0) == -1) { sb_debug_dyn("EARLY FAIL: %s(%s): %s\n", func, pathname, strerror(errno)); return false; } diff --git a/libsandbox/wrapper-funcs/fopen_pre_check.c b/libsandbox/wrapper-funcs/fopen_pre_check.c index 95108e0..e3ed2c6 100644 --- a/libsandbox/wrapper-funcs/fopen_pre_check.c +++ b/libsandbox/wrapper-funcs/fopen_pre_check.c @@ -11,7 +11,7 @@ bool sb_fopen_pre_check(const char *func, const char *pathname, const char *mode save_errno(); /* If we're trying to read, fail normally if file does not stat */ - if (faccessat(AT_FDCWD, pathname, F_OK, 0) == -1) { + if (sb_exists(AT_FDCWD, pathname, 0) == -1) { sb_debug_dyn("EARLY FAIL: %s(%s): %s\n", func, pathname, strerror(errno)); return false; diff --git a/libsbutil/local.mk b/libsbutil/local.mk index 126c7ce..1cb5de7 100644 --- a/libsbutil/local.mk +++ b/libsbutil/local.mk @@ -16,6 +16,7 @@ noinst_LTLIBRARIES += %D%/libsbutil.la %D%/environment.c \ %D%/sb_backtrace.c \ %D%/sb_efuncs.c \ + %D%/sb_exists.c \ %D%/sb_gdb.c \ %D%/sb_method.c \ %D%/sb_open.c \ diff --git a/libsbutil/sb_exists.c b/libsbutil/sb_exists.c new file mode 100644 index 0000000..9ec7730 --- /dev/null +++ b/libsbutil/sb_exists.c @@ -0,0 +1,24 @@ +/* + * Copyright 2023 Gentoo Authors + * Distributed under the terms of the GNU General Public License v2 + */ + +#include "headers.h" +#include "sbutil.h" + +/* Wrapper for faccessat to work around buggy behavior on musl */ +int sb_exists(int dirfd, const char *pathname, int flags) +{ + struct stat64 buf; + + if (faccessat(dirfd, pathname, F_OK, flags) == 0) + return 0; + + /* musl's faccessat gives EINVAL when the kernel does not support + * faccessat2 and AT_SYMLINK_NOFOLLOW is set. + * https://www.openwall.com/lists/musl/2023/06/19/1 */ + if (errno != EINVAL) + return -1; + + return fstatat64(dirfd, pathname, &buf, flags); +} diff --git a/libsbutil/sbutil.h b/libsbutil/sbutil.h index c146b80..4061dd3 100644 --- a/libsbutil/sbutil.h +++ b/libsbutil/sbutil.h @@ -111,6 +111,7 @@ size_t sb_write(int fd, const void *buf, size_t count); int sb_close(int fd); void sb_close_all_fds(void); int sb_copy_file_to_fd(const char *file, int ofd); +int sb_exists(int dirfd, const char *pathname, int flags); /* Reliable output */ __printf(1, 2) void sb_printf(const char *format, ...); diff --git a/libsbutil/src/file.c b/libsbutil/src/file.c index 5a361f4..64a6f0e 100644 --- a/libsbutil/src/file.c +++ b/libsbutil/src/file.c @@ -15,7 +15,7 @@ bool rc_file_exists (const char *pathname) { - return faccessat(AT_FDCWD, pathname, F_OK, AT_SYMLINK_NOFOLLOW) == 0; + return sb_exists(AT_FDCWD, pathname, AT_SYMLINK_NOFOLLOW) == 0; } bool
