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authorRishabh Dave <ridave@redhat.com>2024-02-01 17:07:16 +0530
committerIlya Dryomov <idryomov@gmail.com>2024-02-07 14:58:02 +0100
commitcda4672da1c26835dcbd7aec2bfed954eda9b5ef (patch)
tree5c25c5424be2479f8a6355019e7fcb9b9c9f67a8
parentbbb20ea993f46743f7429092ddc52f1a5c5428ef (diff)
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ceph: prevent use-after-free in encode_cap_msg()
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@vger.kernel.org Link: https://tracker.ceph.com/issues/59259 Signed-off-by: Rishabh Dave <ridave@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> Reviewed-by: Xiubo Li <xiubli@redhat.com> Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
-rw-r--r--fs/ceph/caps.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 9c02f328c966..e8bf082105d8 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -1452,7 +1452,7 @@ static void __prep_cap(struct cap_msg_args *arg, struct ceph_cap *cap,
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;
@@ -1553,6 +1553,7 @@ static void __send_cap(struct cap_msg_args *arg, struct ceph_inode_info *ci)
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);
}