open(O_NOFOLLOW) error when encountered symlink
Jilles Tjoelker
jilles at stack.nl
Sat Mar 12 19:31:36 UTC 2011
On Sat, Mar 12, 2011 at 07:01:23PM +0200, Kostik Belousov wrote:
> Hello,
> I noted the following discussion and commits in the gnu tar repository:
> http://lists.gnu.org/archive/html/bug-tar/2010-11/msg00080.html
>
> http://git.savannah.gnu.org/cgit/tar.git/commit/?id=1584b72ff271e7f826dd64d7a1c7cd2f66504acb
> http://git.savannah.gnu.org/cgit/tar.git/commit/?id=649b747913d2b289e904b5f1d222af886acd209c
> The issue is that in case of open(path, O_NOFOLLOW), when path is naming
> a symlink, FreeBSD returns EMLINK error. On the other hand, the POSIX
> requirement is absolutely clear that it shall be ELOOP.
> I found FreeBSD commit r35088 that specifically changed the error code
> from the required ELOOP to EMLINK. I doubt that somebody can remember
> a reason for the change done more then 12 years ago.
In fact that change was done hours after the new ELOOP error.
> Anybody have strong objections against the patch below ?
Although it loses information (ELOOP may also be caused by the directory
prefix), I think we should make the change.
Please move the error condition in open.2 below the other [ELOOP] error.
usr.bin/cmp relies on the EMLINK error for the -h option and needs some
adjustment. If ELOOP is returned and O_NOFOLLOW is in use, it needs to
check using lstat() if the file is a symlink.
> diff --git a/lib/libc/sys/open.2 b/lib/libc/sys/open.2
> index deca8bc..20877b5 100644
> --- a/lib/libc/sys/open.2
> +++ b/lib/libc/sys/open.2
> @@ -318,7 +318,7 @@ is specified and the named file would reside on a read-only file system.
> The process has already reached its limit for open file descriptors.
> .It Bq Er ENFILE
> The system file table is full.
> -.It Bq Er EMLINK
> +.It Bq Er ELOOP
> .Dv O_NOFOLLOW
> was specified and the target is a symbolic link.
> .It Bq Er ENXIO
> diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
> index 7b5cad1..c7985ef 100644
> --- a/sys/kern/vfs_vnops.c
> +++ b/sys/kern/vfs_vnops.c
> @@ -194,7 +194,7 @@ restart:
> vp = ndp->ni_vp;
> }
> if (vp->v_type == VLNK) {
> - error = EMLINK;
> + error = ELOOP;
> goto bad;
> }
> if (vp->v_type == VSOCK) {
--
Jilles Tjoelker
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