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H A D | dir.c | 5e127580 Wed Oct 31 06:15:23 CDT 2018 Miklos Szeredi <mszeredi@redhat.com> ovl: check whiteout in ovl_create_over_whiteout()
Kaixuxia repors that it's possible to crash overlayfs by removing the whiteout on the upper layer before creating a directory over it. This is a reproducer:
mkdir lower upper work merge touch lower/file mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merge rm merge/file ls -al merge/file rm upper/file ls -al merge/ mkdir merge/file
Before commencing with a vfs_rename(..., RENAME_EXCHANGE) verify that the lookup of "upper" is positive and is a whiteout, and return ESTALE otherwise.
Reported by: kaixuxia <xiakaixu1987@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Fixes: e9be9d5e76e3 ("overlay filesystem") Cc: <stable@vger.kernel.org> # v3.18 5e127580 Wed Oct 31 06:15:23 CDT 2018 Miklos Szeredi <mszeredi@redhat.com> ovl: check whiteout in ovl_create_over_whiteout() Kaixuxia repors that it's possible to crash overlayfs by removing the whiteout on the upper layer before creating a directory over it. This is a reproducer: mkdir lower upper work merge touch lower/file mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merge rm merge/file ls -al merge/file rm upper/file ls -al merge/ mkdir merge/file Before commencing with a vfs_rename(..., RENAME_EXCHANGE) verify that the lookup of "upper" is positive and is a whiteout, and return ESTALE otherwise. Reported by: kaixuxia <xiakaixu1987@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Fixes: e9be9d5e76e3 ("overlay filesystem") Cc: <stable@vger.kernel.org> # v3.18
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