[PULL 1/1] 9pfs: local: read native symlinks when security-model=mapped

[PULL 1/1] 9pfs: local: read native symlinks when security-model=mapped

[Christian Schoenebeck]

From: Andrey Erokhin <language.lawyer@gmail.com>

Directories attached using virtfs with security-model=mapped
may contain native symlinks

This can happen e.g. when booting from a rootfs directory tree
(usually with a writable overlay set up on the host side)

Currently, when security-model=mapped[-xattr|-file],
QEMU assumes that host-side "symlinks" are in the mapped format,
i.e. are regular files storing the linked path,
so it tries to open with O_NOFOLLOW
and fails with ELOOP on native symlinks

This patch introduces a fallback for such cases:
reuse security-model=[none|passthrough] else if branch logic
where readlink will be called for the path basename

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/173
Signed-off-by: Andrey Erokhin <language.lawyer@gmail.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Link: https://lore.kernel.org/qemu-devel/3c35955d-a57e-4203-81c5-395146e23f83@gmail.com
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
---
 hw/9pfs/9p-local.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index c3745f2839..24cb1da90a 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -469,12 +469,16 @@ static ssize_t local_readlink(FsContext *fs_ctx, V9fsPath *fs_path,
 
         fd = local_open_nofollow(fs_ctx, fs_path->data, O_RDONLY, 0);
         if (fd == -1) {
+            if (errno == ELOOP) {
+                goto native_symlink;
+            }
             return -1;
         }
         tsize = RETRY_ON_EINTR(read(fd, (void *)buf, bufsz));
         close_preserve_errno(fd);
     } else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) ||
                (fs_ctx->export_flags & V9FS_SM_NONE)) {
+    native_symlink:;
         char *dirpath = g_path_get_dirname(fs_path->data);
         char *name = g_path_get_basename(fs_path->data);
         int dirfd;
-- 
2.47.3

[PULL 0/1] 9p queue 2026-02-07

[Christian Schoenebeck]

The following changes since commit cd5a79dc98e3087e7658e643bdbbb0baec77ac8a:

  Merge tag 'for_upstream' of https://git.kernel.org/pub/scm/virt/kvm/mst/qemu into staging (2026-02-05 13:54:50 +0000)

are available in the Git repository at:

  https://github.com/cschoenebeck/qemu.git tags/pull-9p-20260207

for you to fetch changes up to 22296f2db9f17f9954f85de9e99b09498936eb51:

  9pfs: local: read native symlinks when security-model=mapped (2026-02-07 13:38:56 +0100)

----------------------------------------------------------------
9pfs changes:

* security-model=mapped: add fallback for reading native symlink
  (if no mapped symlink present).

----------------------------------------------------------------
Andrey Erokhin (1):
      9pfs: local: read native symlinks when security-model=mapped

 hw/9pfs/9p-local.c | 4 ++++
 1 file changed, 4 insertions(+)

Re: [PULL 0/1] 9p queue 2026-02-07

[Peter Maydell]

On Sat, 7 Feb 2026 at 13:23, Christian Schoenebeck
<qemu_oss@crudebyte.com> wrote:
>
> The following changes since commit cd5a79dc98e3087e7658e643bdbbb0baec77ac8a:
>
>   Merge tag 'for_upstream' of https://git.kernel.org/pub/scm/virt/kvm/mst/qemu into staging (2026-02-05 13:54:50 +0000)
>
> are available in the Git repository at:
>
>   https://github.com/cschoenebeck/qemu.git tags/pull-9p-20260207
>
> for you to fetch changes up to 22296f2db9f17f9954f85de9e99b09498936eb51:
>
>   9pfs: local: read native symlinks when security-model=mapped (2026-02-07 13:38:56 +0100)
>
> ----------------------------------------------------------------
> 9pfs changes:
>
> * security-model=mapped: add fallback for reading native symlink
>   (if no mapped symlink present).
>



Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/11.0
for any user-visible changes.

-- PMM