From: Marc Dionne marc.dionne@auristor.com
[ Upstream commit 29be9100aca2915fab54b5693309bc42956542e5 ]
Don't cross a mountpoint that explicitly specifies a backup volume (target is <vol>.backup) when starting from a backup volume.
It it not uncommon to mount a volume's backup directly in the volume itself. This can cause tools that are not paying attention to get into a loop mounting the volume onto itself as they attempt to traverse the tree, leading to a variety of problems.
This doesn't prevent the general case of loops in a sequence of mountpoints, but addresses a common special case in the same way as other afs clients.
Reported-by: Jan Henrik Sylvester jan.henrik.sylvester@uni-hamburg.de Link: http://lists.infradead.org/pipermail/linux-afs/2024-May/008454.html Reported-by: Markus Suvanto markus.suvanto@gmail.com Link: http://lists.infradead.org/pipermail/linux-afs/2024-February/008074.html Signed-off-by: Marc Dionne marc.dionne@auristor.com Signed-off-by: David Howells dhowells@redhat.com Link: https://lore.kernel.org/r/768760.1716567475@warthog.procyon.org.uk Reviewed-by: Jeffrey Altman jaltman@auristor.com cc: linux-afs@lists.infradead.org Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/afs/mntpt.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c index 97f50e9fd9eb0..297487ee83231 100644 --- a/fs/afs/mntpt.c +++ b/fs/afs/mntpt.c @@ -140,6 +140,11 @@ static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt) put_page(page); if (ret < 0) return ret; + + /* Don't cross a backup volume mountpoint from a backup volume */ + if (src_as->volume && src_as->volume->type == AFSVL_BACKVOL && + ctx->type == AFSVL_BACKVOL) + return -ENODEV; }
return 0;