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std: fix unix socket address truncation without a trailing NUL #160416

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Merged
rust-bors merged 1 commit into from
Aug 17, 2026
Merged

std: fix unix socket address truncation without a trailing NUL #160416

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10 changes: 4 additions & 6 deletions library/std/src/os/unix/net/addr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -255,12 +255,10 @@ impl SocketAddr {
} else if self.addr.sun_path[0] == 0 {
AddressKind::Abstract(ByteStr::from_bytes(&path[1..len]))
} else {
// the value returned by getsockname(2) and similar on QNX7.1 and
// QNX8 does not count the NUL byte terminator of the path string,
// which matches the behavior of the SUN_LEN macro in libc, but
// other OSes do count the NUL byte so adjust accordingly
let end =
if cfg!(any(target_os = "qnx", target_env = "nto71")) { len } else { len - 1 };
// linux adds a trailing NUL and counts it in the length, freebsd, netbsd
// and qnx do not, and a caller may bind(2) without one either. unix(7)
// gives the portable rule: strnlen(sun_path, len - offsetof(sun_path))

@Mark-Simulacrum Mark-Simulacrum Aug 8, 2026 •
edited by rustbot
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Should this also adjust

rust/library/std/src/os/unix/net/addr.rs

Lines 57 to 63 in 771916f

// on QNX7.1 and QNX8 the `len` value returned by the SUN_LEN
// macro in its libc does not include the null byte in the count so
// don't add it here to match what a C program passes to bind(2) and
// similar functions
if cfg!(not(any(target_os = "qnx", target_env = "nto71"))) {
len += 1
}
? Haven't traced the code but went looking for the QNX modifications which were in #158697.

View changes since the review

@devnexen devnexen Aug 15, 2026

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no because only the inbound one was a parsing bug, "oddly" enough QNX has it right using len (because this platform excludes the NULL terminator). As for the 'cfg' part, it is still needed as len is fed to bind where SUN_LEN for QNX is a real kernel-facing difference.

@devnexen devnexen Aug 15, 2026

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@rustbot ready

let end = core::slice::memchr::memchr(0, &path[..len]).unwrap_or(len);
AddressKind::Pathname(OsStr::from_bytes(&path[..end]).as_ref())
}
}
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23 changes: 23 additions & 0 deletions library/std/src/os/unix/net/tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,29 @@ fn sock_addr_from_pathname() {
assert_eq!(address.as_pathname(), Some(Path::new("/path/to/socket")));
}

// the trailing NUL is not counted in the reported length on freebsd, netbsd
// and qnx, and a caller may bind(2) without one anywhere
#[test]
fn sock_addr_without_trailing_nul() {
const PATH: &[u8] = b"/path/to/socket";

// SAFETY: all zeros is a valid representation for `sockaddr_un`.
let mut addr: libc::sockaddr_un = unsafe { crate::mem::zeroed() };
addr.sun_family = libc::AF_UNIX as libc::sa_family_t;
for (dst, &src) in addr.sun_path.iter_mut().zip(PATH) {
*dst = src as _;
}
let offset = crate::mem::offset_of!(libc::sockaddr_un, sun_path);

// length excluding the NUL, as reported by freebsd, netbsd and qnx
let address = or_panic!(SocketAddr::from_parts(addr, (offset + PATH.len()) as _));
assert_eq!(address.as_pathname(), Some(Path::new("/path/to/socket")));

// length including the NUL, as reported by linux
let address = or_panic!(SocketAddr::from_parts(addr, (offset + PATH.len() + 1) as _));
assert_eq!(address.as_pathname(), Some(Path::new("/path/to/socket")));
}

#[test]
#[cfg_attr(target_os = "android", ignore)] // Android SELinux rules prevent creating Unix sockets
#[cfg_attr(target_os = "vxworks", ignore = "Unix sockets are not implemented in VxWorks")]
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