| Message ID | a5547a1af1dc90d65100c873204a5b0912ecb9a8.1618563564.git.ps@pks.im (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fix `statx()` emulation breaking exports | expand |
On 4/16/21 5:00 AM, Patrick Steinhardt wrote: > 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@pks.im> Committed (tag: nfs-utils-2-5-4-rc3) steved. > --- > 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); > } > >
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); }
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@pks.im> --- support/misc/xstat.c | 2 ++ 1 file changed, 2 insertions(+)