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fs: Pass AT_GETATTR_NOSEC flag to getattr interface function
When vfs_getattr_nosec() calls a filesystem's getattr interface function then the 'nosec' should propagate into this function so that vfs_getattr_nosec() can again be called from the filesystem's gettattr rather than vfs_getattr(). The latter would add unnecessary security checks that the initial vfs_getattr_nosec() call wanted to avoid. Therefore, introduce the getattr flag GETATTR_NOSEC and allow to pass with the new getattr_flags parameter to the getattr interface function. In overlayfs and ecryptfs use this flag to determine which one of the two functions to call. In a recent code change introduced to IMA vfs_getattr_nosec() ended up calling vfs_getattr() in overlayfs, which in turn called security_inode_getattr() on an exiting process that did not have current->fs set anymore, which then caused a kernel NULL pointer dereference. With this change the call to security_inode_getattr() can be avoided, thus avoiding the NULL pointer dereference. Reported-by: <syzbot+a67fc5321ffb4b311c98@syzkaller.appspotmail.com> Fixes: db1d1e8 ("IMA: use vfs_getattr_nosec to get the i_version") Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: <linux-fsdevel@vger.kernel.org> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: Amir Goldstein <amir73il@gmail.com> Cc: Tyler Hicks <code@tyhicks.com> Cc: Mimi Zohar <zohar@linux.ibm.com> Suggested-by: Christian Brauner <brauner@kernel.org> Co-developed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com> Link: https://lore.kernel.org/r/20231002125733.1251467-1-stefanb@linux.vnet.ibm.com Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Christian Brauner <brauner@kernel.org>
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Stefan Berger
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Christian Brauner
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Nov 18, 2023
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