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posix_acl: Clear SGID bit when setting file permissions
When file permissions are modified via chmod(2) and the user is not in the owning group or capable of CAP_FSETID, the setgid bit is cleared in inode_change_ok(). Setting a POSIX ACL via setxattr(2) sets the file permissions as well as the new ACL, but doesn't clear the setgid bit in a similar way; this allows to bypass the check in chmod(2). Fix that. References: CVE-2016-7097 Reviewed-by: Christoph Hellwig <[email protected]> Reviewed-by: Jeff Layton <[email protected]> Signed-off-by: Jan Kara <[email protected]> Signed-off-by: Andreas Gruenbacher <[email protected]>
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parent
5d3ddd84ea
commit
073931017b
16 changed files with 89 additions and 102 deletions
40
fs/9p/acl.c
40
fs/9p/acl.c
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@ -276,32 +276,26 @@ static int v9fs_xattr_set_acl(const struct xattr_handler *handler,
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switch (handler->flags) {
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case ACL_TYPE_ACCESS:
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if (acl) {
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umode_t mode = inode->i_mode;
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retval = posix_acl_equiv_mode(acl, &mode);
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if (retval < 0)
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struct iattr iattr;
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retval = posix_acl_update_mode(inode, &iattr.ia_mode, &acl);
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if (retval)
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goto err_out;
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else {
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struct iattr iattr;
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if (retval == 0) {
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/*
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* ACL can be represented
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* by the mode bits. So don't
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* update ACL.
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*/
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acl = NULL;
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value = NULL;
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size = 0;
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}
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/* Updte the mode bits */
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iattr.ia_mode = ((mode & S_IALLUGO) |
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(inode->i_mode & ~S_IALLUGO));
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iattr.ia_valid = ATTR_MODE;
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/* FIXME should we update ctime ?
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* What is the following setxattr update the
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* mode ?
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if (!acl) {
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/*
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* ACL can be represented
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* by the mode bits. So don't
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* update ACL.
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*/
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v9fs_vfs_setattr_dotl(dentry, &iattr);
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value = NULL;
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size = 0;
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}
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iattr.ia_valid = ATTR_MODE;
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/* FIXME should we update ctime ?
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* What is the following setxattr update the
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* mode ?
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*/
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v9fs_vfs_setattr_dotl(dentry, &iattr);
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}
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break;
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case ACL_TYPE_DEFAULT:
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