Skip to content

Commit

Permalink
Don't use env::current_exe with libbacktrace
Browse files Browse the repository at this point in the history
If the path we give to libbacktrace doesn't actually correspond to the
current process, libbacktrace will segfault *at best*.

cc rust-lang#21889
  • Loading branch information
sfackler committed May 11, 2016
1 parent 6dbb0e8 commit 9c2e691
Show file tree
Hide file tree
Showing 2 changed files with 21 additions and 42 deletions.
49 changes: 12 additions & 37 deletions src/libstd/sys/common/gnu/libbacktrace.rs
Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,6 @@ use sys_common::backtrace::{output, output_fileline};

pub fn print(w: &mut Write, idx: isize, addr: *mut libc::c_void,
symaddr: *mut libc::c_void) -> io::Result<()> {
use env;
use ffi::CStr;
use ptr;

Expand Down Expand Up @@ -110,46 +109,22 @@ pub fn print(w: &mut Write, idx: isize, addr: *mut libc::c_void,
// that is calculated the first time this is requested. Remember that
// backtracing all happens serially (one global lock).
//
// An additionally oddity in this function is that we initialize the
// filename via self_exe_name() to pass to libbacktrace. It turns out
// that on Linux libbacktrace seamlessly gets the filename of the
// current executable, but this fails on freebsd. by always providing
// it, we make sure that libbacktrace never has a reason to not look up
// the symbols. The libbacktrace API also states that the filename must
// be in "permanent memory", so we copy it to a static and then use the
// static as the pointer.
// Things don't work so well on not-Linux since libbacktrace can't track
// down that executable this is. We at one point used env::current_exe but
// it turns out that there are some serious security issues with that
// approach.
//
// FIXME: We also call self_exe_name() on DragonFly BSD. I haven't
// tested if this is required or not.
// Specifically, on certain platforms like BSDs, a malicious actor can cause
// an arbitrary file to be placed at the path returned by current_exe.
// libbacktrace does not behave defensively in the presence of ill-formed
// DWARF information, and has been demonstrated to segfault in at least one
// case. There is no evidence at the moment to suggest that a more carefully
// constructed file can't cause arbitrary code execution. As a result of all
// of this, we don't hint libbacktrace with the path to the current process.
unsafe fn init_state() -> *mut backtrace_state {
static mut STATE: *mut backtrace_state = ptr::null_mut();
static mut LAST_FILENAME: [libc::c_char; 256] = [0; 256];
if !STATE.is_null() { return STATE }
let selfname = if cfg!(target_os = "freebsd") ||
cfg!(target_os = "dragonfly") ||
cfg!(target_os = "bitrig") ||
cfg!(target_os = "openbsd") ||
cfg!(target_os = "windows") {
env::current_exe().ok()
} else {
None
};
let filename = match selfname.as_ref().and_then(|s| s.to_str()) {
Some(path) => {
let bytes = path.as_bytes();
if bytes.len() < LAST_FILENAME.len() {
let i = bytes.iter();
for (slot, val) in LAST_FILENAME.iter_mut().zip(i) {
*slot = *val as libc::c_char;
}
LAST_FILENAME.as_ptr()
} else {
ptr::null()
}
}
None => ptr::null(),
};
STATE = backtrace_create_state(filename, 0, error_cb,
STATE = backtrace_create_state(ptr::null(), 0, error_cb,
ptr::null_mut());
STATE
}
Expand Down
14 changes: 9 additions & 5 deletions src/test/run-pass/backtrace-debuginfo.rs
Original file line number Diff line number Diff line change
Expand Up @@ -32,11 +32,15 @@ macro_rules! dump_and_die {
($($pos:expr),*) => ({
// FIXME(#18285): we cannot include the current position because
// the macro span takes over the last frame's file/line.
if cfg!(target_os = "macos") ||
cfg!(target_os = "ios") ||
cfg!(target_os = "android") ||
cfg!(all(target_os = "linux", target_arch = "arm")) ||
cfg!(all(windows, target_env = "gnu")) {
if cfg!(any(target_os = "macos",
target_os = "ios",
target_os = "android",
all(target_os = "linux", target_arch = "arm"),
target_os = "windows",
target_os = "freebsd",
target_os = "dragonfly",
target_os = "bitrig",
target_os = "openbsd")) {
// skip these platforms as this support isn't implemented yet.
} else {
dump_filelines(&[$($pos),*]);
Expand Down

0 comments on commit 9c2e691

Please sign in to comment.