From: Danilo Krummrich <dakr@redhat.com>
To: ojeda@kernel.org, alex.gaynor@gmail.com, wedsonaf@gmail.com,
boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com,
benno.lossin@proton.me, a.hindborg@samsung.com,
aliceryhl@google.com
Cc: rust-for-linux@vger.kernel.org, Danilo Krummrich <dakr@redhat.com>
Subject: [PATCH] rust: alloc: fix dangling pointer in VecExt<T>::reserve()
Date: Mon, 29 Apr 2024 21:24:04 +0200 [thread overview]
Message-ID: <20240429192435.2235-1-dakr@redhat.com> (raw)
Currently, a Vec<T>'s ptr value, after calling Vec<T>::new(), is
initialized to Unique::dangling(). Hence, in VecExt<T>::reserve(), we're
passing a dangling pointer (instead of NULL) to krealloc() whenever a
new Vec<T> is created through VecExt<T> extension functions.
This only works since it happens that Unique::dangling()'s value (0x1)
falls within the range between 0x0 and ZERO_SIZE_PTR (0x10) and
krealloc() hence treats it the same as a NULL pointer however.
This isn't a case we should rely on, especially since other kernel
allocators are not as tolerant. Instead, pass a real NULL pointer to
krealloc_aligned() if Vec<T>'s capacity is zero.
Fixes: 5ab560ce12ed ("rust: alloc: update `VecExt` to take allocation flags")
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
---
rust/kernel/alloc/vec_ext.rs | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/rust/kernel/alloc/vec_ext.rs b/rust/kernel/alloc/vec_ext.rs
index 6a916fcf8bf1..ffcf8a19f715 100644
--- a/rust/kernel/alloc/vec_ext.rs
+++ b/rust/kernel/alloc/vec_ext.rs
@@ -4,6 +4,7 @@
use super::{AllocError, Flags};
use alloc::vec::Vec;
+use core::ptr;
use core::result::Result;
/// Extensions to [`Vec`].
@@ -137,6 +138,15 @@ fn reserve(&mut self, additional: usize, flags: Flags) -> Result<(), AllocError>
let (ptr, len, cap) = destructure(self);
+ // We need to make sure that ptr is either NULL or comes from a previous call to
+ // `krealloc_aligned`. A `Vec<T>`'s `ptr` value is not guaranteed to be NULL and might be
+ // dangling after being created with `Vec::new`. Instead, we can rely on `Vec<T>'s capacity
+ // to be zero if no memory has been allocated yet.
+ let ptr = match cap {
+ 0 => ptr::null_mut(),
+ _ => ptr,
+ };
+
// SAFETY: `ptr` is valid because it's either NULL or comes from a previous call to
// `krealloc_aligned`. We also verified that the type is not a ZST.
let new_ptr = unsafe { super::allocator::krealloc_aligned(ptr.cast(), layout, flags) };
base-commit: 2c1092853f163762ef0aabc551a630ef233e1be3
--
2.44.0
next reply other threads:[~2024-04-29 19:24 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-29 19:24 Danilo Krummrich [this message]
2024-04-29 19:52 ` [PATCH] rust: alloc: fix dangling pointer in VecExt<T>::reserve() Boqun Feng
2024-04-29 21:01 ` Danilo Krummrich
2024-04-29 22:01 ` Boqun Feng
2024-04-30 16:42 ` Danilo Krummrich
2024-04-30 18:33 ` Boqun Feng
2024-04-30 20:46 ` Danilo Krummrich
2024-04-30 20:59 ` Boqun Feng
2024-04-30 21:08 ` Boqun Feng
2024-04-30 22:19 ` Danilo Krummrich
2024-04-30 22:41 ` Boqun Feng
2024-04-30 22:06 ` Boqun Feng
2024-04-30 22:44 ` Miguel Ojeda
2024-04-30 8:25 ` Alice Ryhl
2024-04-30 12:07 ` Danilo Krummrich
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240429192435.2235-1-dakr@redhat.com \
--to=dakr@redhat.com \
--cc=a.hindborg@samsung.com \
--cc=alex.gaynor@gmail.com \
--cc=aliceryhl@google.com \
--cc=benno.lossin@proton.me \
--cc=bjorn3_gh@protonmail.com \
--cc=boqun.feng@gmail.com \
--cc=gary@garyguo.net \
--cc=ojeda@kernel.org \
--cc=rust-for-linux@vger.kernel.org \
--cc=wedsonaf@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).