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56ad3e54da
The local_lgetxattr() callback is vulnerable to symlink attacks because it calls lgetxattr() which follows symbolic links in all path elements but the rightmost one. This patch introduces a helper to emulate the non-existing fgetxattrat() function: it is implemented with /proc/self/fd which provides a trusted path that can be safely passed to lgetxattr(). local_lgetxattr() is converted to use this helper and opendir_nofollow(). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz <groug@kaod.org> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
53 lines
1.2 KiB
C
53 lines
1.2 KiB
C
/*
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* 9p utilities
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*
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* Copyright IBM, Corp. 2017
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*
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* Authors:
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* Greg Kurz <groug@kaod.org>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#ifndef QEMU_9P_UTIL_H
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#define QEMU_9P_UTIL_H
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static inline void close_preserve_errno(int fd)
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{
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int serrno = errno;
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close(fd);
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errno = serrno;
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}
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static inline int openat_dir(int dirfd, const char *name)
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{
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return openat(dirfd, name, O_DIRECTORY | O_RDONLY | O_PATH);
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}
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static inline int openat_file(int dirfd, const char *name, int flags,
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mode_t mode)
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{
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int fd, serrno, ret;
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fd = openat(dirfd, name, flags | O_NOFOLLOW | O_NOCTTY | O_NONBLOCK,
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mode);
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if (fd == -1) {
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return -1;
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}
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serrno = errno;
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/* O_NONBLOCK was only needed to open the file. Let's drop it. */
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ret = fcntl(fd, F_SETFL, flags);
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assert(!ret);
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errno = serrno;
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return fd;
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}
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int relative_openat_nofollow(int dirfd, const char *path, int flags,
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mode_t mode);
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ssize_t fgetxattrat_nofollow(int dirfd, const char *path, const char *name,
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void *value, size_t size);
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#endif
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