This is a note to let you know that I've just added the patch titled
ceph: prevent use-after-free in encode_cap_msg()
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ceph-prevent-use-after-free-in-encode_cap_msg.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From cda4672da1c26835dcbd7aec2bfed954eda9b5ef Mon Sep 17 00:00:00 2001
From: Rishabh Dave <ridave@xxxxxxxxxx>
Date: Thu, 1 Feb 2024 17:07:16 +0530
Subject: ceph: prevent use-after-free in encode_cap_msg()
From: Rishabh Dave <ridave@xxxxxxxxxx>
commit cda4672da1c26835dcbd7aec2bfed954eda9b5ef upstream.
In fs/ceph/caps.c, in encode_cap_msg(), "use after free" error was
caught by KASAN at this line - 'ceph_buffer_get(arg->xattr_buf);'. This
implies before the refcount could be increment here, it was freed.
In same file, in "handle_cap_grant()" refcount is decremented by this
line - 'ceph_buffer_put(ci->i_xattrs.blob);'. It appears that a race
occurred and resource was freed by the latter line before the former
line could increment it.
encode_cap_msg() is called by __send_cap() and __send_cap() is called by
ceph_check_caps() after calling __prep_cap(). __prep_cap() is where
arg->xattr_buf is assigned to ci->i_xattrs.blob. This is the spot where
the refcount must be increased to prevent "use after free" error.
Cc: stable@xxxxxxxxxxxxxxx
Link: https://tracker.ceph.com/issues/59259
Signed-off-by: Rishabh Dave <ridave@xxxxxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Reviewed-by: Xiubo Li <xiubli@xxxxxxxxxx>
Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ceph/caps.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -1391,7 +1391,7 @@ static void __prep_cap(struct cap_msg_ar
if (flushing & CEPH_CAP_XATTR_EXCL) {
arg->old_xattr_buf = __ceph_build_xattrs_blob(ci);
arg->xattr_version = ci->i_xattrs.version;
- arg->xattr_buf = ci->i_xattrs.blob;
+ arg->xattr_buf = ceph_buffer_get(ci->i_xattrs.blob);
} else {
arg->xattr_buf = NULL;
arg->old_xattr_buf = NULL;
@@ -1457,6 +1457,7 @@ static void __send_cap(struct cap_msg_ar
encode_cap_msg(msg, arg);
ceph_con_send(&arg->session->s_con, msg);
ceph_buffer_put(arg->old_xattr_buf);
+ ceph_buffer_put(arg->xattr_buf);
if (arg->wake)
wake_up_all(&ci->i_cap_wq);
}
Patches currently in stable-queue which might be from ridave@xxxxxxxxxx are
queue-6.1/ceph-prevent-use-after-free-in-encode_cap_msg.patch
