46 lines
1.6 KiB
Diff
46 lines
1.6 KiB
Diff
From: Al Viro <viro@zeniv.linux.org.uk>
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Date: Mon, 27 Apr 2020 10:26:22 -0400
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Subject: propagate_one(): mnt_set_mountpoint() needs mount_lock
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Origin: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit?id=fa87bf609aa173b5dce91d23cd3dcebd9e846124
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commit b0d3869ce9eeacbb1bbd541909beeef4126426d5 upstream.
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... to protect the modification of mp->m_count done by it. Most of
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the places that modify that thing also have namespace_lock held,
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but not all of them can do so, so we really need mount_lock here.
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Kudos to Piotr Krysiuk <piotras@gmail.com>, who'd spotted a related
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bug in pivot_root(2) (fixed unnoticed in 5.3); search for other
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similar turds has caught out this one.
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Cc: stable@kernel.org
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Piotr Krysiuk <piotras@gmail.com>
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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---
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fs/pnode.c | 9 ++++-----
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1 file changed, 4 insertions(+), 5 deletions(-)
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diff --git a/fs/pnode.c b/fs/pnode.c
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index 53d411a371ce..7910ae91f17e 100644
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--- a/fs/pnode.c
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+++ b/fs/pnode.c
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@@ -266,14 +266,13 @@ static int propagate_one(struct mount *m)
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if (IS_ERR(child))
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return PTR_ERR(child);
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child->mnt.mnt_flags &= ~MNT_LOCKED;
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+ read_seqlock_excl(&mount_lock);
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mnt_set_mountpoint(m, mp, child);
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+ if (m->mnt_master != dest_master)
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+ SET_MNT_MARK(m->mnt_master);
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+ read_sequnlock_excl(&mount_lock);
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last_dest = m;
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last_source = child;
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- if (m->mnt_master != dest_master) {
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- read_seqlock_excl(&mount_lock);
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- SET_MNT_MARK(m->mnt_master);
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- read_sequnlock_excl(&mount_lock);
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- }
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hlist_add_head(&child->mnt_hash, list);
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return count_mounts(m->mnt_ns, child);
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}
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