diff options
authorRich Felker <>2020-09-09 21:55:11 -0400
committerRich Felker <>2020-09-09 21:55:11 -0400
commit55fb9a177316aa46c639d93dd0323d9a9a8c160c (patch)
parentf035c7b1e65b6566c979ed69bada82a466580ba2 (diff)
use new SYS_faccessat2 syscall to implement faccessat with flags
commit 0a05eace163cee9b08571d2ff9d90f5e82d9c228 implemented AT_EACCESS for faccessat with a horrible hack, creating a child process to change switch uid/gid and perform the access probe without making potentially irreversible changes to the caller's credentials. this was due to the syscall lacking a flags argument. linux 5.8 introduced a new syscall, SYS_faccessat2, fixing this deficiency. use it if any flags are passed, and fallback to the old strategy on ENOSYS. continue using the old syscall when there are no flags.
1 files changed, 8 insertions, 3 deletions
diff --git a/src/unistd/faccessat.c b/src/unistd/faccessat.c
index 76bbd4c7..557503eb 100644
--- a/src/unistd/faccessat.c
+++ b/src/unistd/faccessat.c
@@ -25,12 +25,17 @@ static int checker(void *p)
int faccessat(int fd, const char *filename, int amode, int flag)
- if (!flag || (flag==AT_EACCESS && getuid()==geteuid() && getgid()==getegid()))
- return syscall(SYS_faccessat, fd, filename, amode, flag);
+ if (flag) {
+ int ret = __syscall(SYS_faccessat2, fd, filename, amode, flag);
+ if (ret != -ENOSYS) return __syscall_ret(ret);
+ }
- if (flag != AT_EACCESS)
+ if (flag & ~AT_EACCESS)
return __syscall_ret(-EINVAL);
+ if (!flag || (getuid()==geteuid() && getgid()==getegid()))
+ return syscall(SYS_faccessat, fd, filename, amode);
char stack[1024];
sigset_t set;
pid_t pid;