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commitc9cc8d01fbupstream. If devpts_ptmx_path() returns an error code, then devpts_mntget() dereferences an ERR_PTR(): BUG: unable to handle kernel paging request at fffffffffffffff5 IP: devpts_mntget+0x13f/0x280 fs/devpts/inode.c:173 Fix it by returning early in the error paths. Reproducer: #define _GNU_SOURCE #include <fcntl.h> #include <sched.h> #include <sys/ioctl.h> #define TIOCGPTPEER _IO('T', 0x41) int main() { for (;;) { int fd = open("/dev/ptmx", 0); unshare(CLONE_NEWNS); ioctl(fd, TIOCGPTPEER, 0); } } Fixes:311fc65c9f("pty: Repair TIOCGPTPEER") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.