s3: VFS: shadow_copy2: Fix usage of saved_errno to only set errno on error.
Rationale:
VFS calls must act like their POSIX equivalents, and the POSIX versions
*only* set errno on a failure. There is actually code in the upper smbd
layers that depends on errno being correct on a fail return from a VFS call.
For a compound VFS module like this, a common pattern is :
SMB_VFS_CALL_X()
{
int ret;
syscall1();
ret = syscall2();
syscall3();
return ret;
}
Where if *any* of the contained syscallX()'s fail, they'll set errno.
However, the actual errno we should return is *only* the one returned
if syscall2() fails (the others are lstat's checking for existence etc.).
So what we should do to correctly return only the errno from syscall2() is:
SMB_VFS_CALL_X()
{
int ret;
int saved_errno = 0;
syscall1()
ret = syscall2();
if (ret == -1) {
saved_errno = errno;
}
syscall3()
if (saved_errno != 0) {
errno = saved_errno;
}
return ret;
}
BUG: https://bugzilla.samba.org/show_bug.cgi?id=12531
Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Uri Simchoni <uri@samba.org>
(backported from commit
cda6764f1a8db96182bfd1855440bc6a1ba1abee)