From: Rishabh Dave <ridave@redhat.com> stable inclusion from stable-v5.15.148 commit 70e329b440762390258a6fe8c0de93c9fdd56c77 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9E2GN CVE: CVE-2024-26689 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=t... -------------------------------- 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@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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Conflicts: fs/ceph/caps.c [__send_cap() has been refacaored] Signed-off-by: Long Li <leo.lilong@huawei.com> --- fs/ceph/caps.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index 1cc433de4200..b631719941c2 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -1347,7 +1347,7 @@ static int __send_cap(struct ceph_mds_client *mdsc, struct ceph_cap *cap, if (flushing & CEPH_CAP_XATTR_EXCL) { old_blob = __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; } @@ -1387,6 +1387,7 @@ static int __send_cap(struct ceph_mds_client *mdsc, struct ceph_cap *cap, dout("error sending cap msg, must requeue %p\n", inode); delayed = 1; } + ceph_buffer_put(arg.xattr_buf); if (wake) wake_up_all(&ci->i_cap_wq); -- 2.39.2