openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 75 insertions, 0 deletions

diff --git a/rust/syn/export.rs b/rust/syn/export.rs
new file mode 100644
index 000000000..05dad324b
--- /dev/null
+++ b/rust/syn/export.rs
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+#[doc(hidden)]
+pub use std::clone::Clone;
+#[doc(hidden)]
+pub use std::cmp::{Eq, PartialEq};
+#[doc(hidden)]
+pub use std::concat;
+#[doc(hidden)]
+pub use std::default::Default;
+#[doc(hidden)]
+pub use std::fmt::Debug;
+#[doc(hidden)]
+pub use std::hash::{Hash, Hasher};
+#[doc(hidden)]
+pub use std::marker::Copy;
+#[doc(hidden)]
+pub use std::option::Option::{None, Some};
+#[doc(hidden)]
+pub use std::result::Result::{Err, Ok};
+#[doc(hidden)]
+pub use std::stringify;
+
+#[doc(hidden)]
+pub type Formatter<'a> = std::fmt::Formatter<'a>;
+#[doc(hidden)]
+pub type FmtResult = std::fmt::Result;
+
+#[doc(hidden)]
+pub type bool = std::primitive::bool;
+#[doc(hidden)]
+pub type str = std::primitive::str;
+
+#[cfg(feature = "printing")]
+#[doc(hidden)]
+pub use quote;
+
+#[doc(hidden)]
+pub type Span = proc_macro2::Span;
+#[doc(hidden)]
+pub type TokenStream2 = proc_macro2::TokenStream;
+
+#[cfg(feature = "parsing")]
+#[doc(hidden)]
+pub use crate::group::{parse_braces, parse_brackets, parse_parens};
+
+#[doc(hidden)]
+pub use crate::span::IntoSpans;
+
+#[cfg(all(feature = "parsing", feature = "printing"))]
+#[doc(hidden)]
+pub use crate::parse_quote::parse as parse_quote;
+
+#[cfg(feature = "parsing")]
+#[doc(hidden)]
+pub use crate::token::parsing::{peek_punct, punct as parse_punct};
+
+#[cfg(feature = "printing")]
+#[doc(hidden)]
+pub use crate::token::printing::punct as print_punct;
+
+#[cfg(feature = "parsing")]
+#[doc(hidden)]
+pub use crate::token::private::CustomToken;
+
+#[cfg(feature = "proc-macro")]
+#[doc(hidden)]
+pub type TokenStream = proc_macro::TokenStream;
+
+#[cfg(feature = "printing")]
+#[doc(hidden)]
+pub use quote::{ToTokens, TokenStreamExt};
+
+#[doc(hidden)]
+pub struct private(pub(crate) ());