Ever since commit 76c21e3f (mountd: Check the stat() return values in match_fsid(), 2020-05-08), it wasn't possible to export filesystems on my musl based system anymore. The root cause of this is the innocuous-looking change to decide based on `errno` whether `is_mountpoint()` raised a real error or whether it simply didn't match. The issue is that `is_mountpoint()` transitively calls into our `xlstat()` wrapper, which either executes `statx()` if the system supports it or otherwise falls back to `fstatat()`. But if `statx()` is not supported, then we'll always first set `errno = ENOSYS` before calling `fstatat()`. So effectively, all systems which do not have `statx()` and whose `fstatat()` doesn't reset `errno` will cause us to end up with errno set to `ENOSYS`. Fix the issue by resetting `errno` before calling `fstatat()` in both `xlstat()` and `xstat()`. Fixes: 76c21e3f (mountd: Check the stat() return values in match_fsid(), 2020-05-08) Signed-off-by: Patrick Steinhardt <ps@xxxxxx> --- support/misc/xstat.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/support/misc/xstat.c b/support/misc/xstat.c index a438fbcc..6f751f7f 100644 --- a/support/misc/xstat.c +++ b/support/misc/xstat.c @@ -85,6 +85,7 @@ int xlstat(const char *pathname, struct stat *statbuf) return 0; else if (errno != ENOSYS) return -1; + errno = 0; return fstatat(AT_FDCWD, pathname, statbuf, AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW); } @@ -95,6 +96,7 @@ int xstat(const char *pathname, struct stat *statbuf) return 0; else if (errno != ENOSYS) return -1; + errno = 0; return fstatat(AT_FDCWD, pathname, statbuf, AT_NO_AUTOMOUNT); } -- 2.31.1
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