From: Marc Dionne <marc.dionne@xxxxxxxxxxxx> [ 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@xxxxxxxxxxxxxx> Link: http://lists.infradead.org/pipermail/linux-afs/2024-May/008454.html Reported-by: Markus Suvanto <markus.suvanto@xxxxxxxxx> Link: http://lists.infradead.org/pipermail/linux-afs/2024-February/008074.html Signed-off-by: Marc Dionne <marc.dionne@xxxxxxxxxxxx> Signed-off-by: David Howells <dhowells@xxxxxxxxxx> Link: https://lore.kernel.org/r/768760.1716567475@xxxxxxxxxxxxxxxxxxxxxx Reviewed-by: Jeffrey Altman <jaltman@xxxxxxxxxxxx> cc: linux-afs@xxxxxxxxxxxxxxxxxxx Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/afs/mntpt.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c index f105f061e89bb..eeb2b4b11e323 100644 --- a/fs/afs/mntpt.c +++ b/fs/afs/mntpt.c @@ -146,6 +146,11 @@ 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; -- 2.43.0
