reef: client: Fix opening and reading of symlinks#60373
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man open(2)[1] says the following for O_PATH: . . . If pathname is a symbolic link and the O_NOFOLLOW flag is also specified, then the call returns a file descriptor referring to the symbolic link. This file descriptor can be used as the dirfd argument in calls to fchownat(2), fstatat(2), linkat(2), and readlinkat(2) with an empty pathname to have the calls operate on the symbolic link. . . . symlink check within may_open() failed to consider the O_PATH flag resulting in a ELOOP error to the client. In order to return a valid file descriptor we introduce a check for the presence of O_PATH in the client provided flags. Fixes: https://tracker.ceph.com/issues/67833 [1] https://www.man7.org/linux/man-pages/man2/open.2.html Signed-off-by: Anoop C S <anoopcs@cryptolab.net> (cherry picked from commit 8443821)
man readlinkat(2)[1] points at a special case for readlinkat() syscall as follows: . . . Since Linux 2.6.39, pathname can be an empty string, in which case the call operates on the symbolic link referred to by dirfd (which should have been obtained using open(2) with the O_PATH and O_NOFOLLOW flags). . . . man open(2)[2] further explains the need for such a special case when a symlink is opened with O_PATH and O_NOFOLLOW: . . . If pathname is a symbolic link and the O_NOFOLLOW flag is also specified, then the call returns a file descriptor referring to the symbolic link. This file descriptor can be used as the dirfd argument in calls to fchownat(2), fstatat(2), linkat(2), and readlinkat(2) with an empty pathname to have the calls operate on the symbolic link. . . . Accordingly have a check to resolve symlinks out of dirfd when empty pathnames are encountered within readlinkat(). In addition to that match the standard file system behavior to return ENOENT instead of EINVAL when the inode pointed to by dirfd is not a symbolic link with empty pathnames. Fixes: https://tracker.ceph.com/issues/67833 [1] https://www.man7.org/linux/man-pages/man2/readlinkat.2.html [2] https://www.man7.org/linux/man-pages/man2/open.2.html Signed-off-by: Anoop C S <anoopcs@cryptolab.net> (cherry picked from commit 24f453d)
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This PR is under test in https://tracker.ceph.com/issues/69503. |
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Can one of the admins verify this patch? |
vshankar
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* refs/pull/60373/head: client: Resolve symlink from dirfd for empty pathname client: Fix symlink open with O_PATH and O_NOFOLLOW
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mchangir
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backport tracker: https://tracker.ceph.com/issues/68574
backport of #59503
parent tracker: https://tracker.ceph.com/issues/67833
this backport was staged using ceph-backport.sh version 16.0.0.6848
find the latest version at https://github.com/ceph/ceph/blob/main/src/script/ceph-backport.sh