systemd/SOURCES/0291-bpf-fix-restrict_fs-on-s390x.patch

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2023-11-07 11:29:40 +00:00
From b544c7bfd7812458516d29a11511498ece02b9ee Mon Sep 17 00:00:00 2001
From: Ilya Leoshkevich <iii@linux.ibm.com>
Date: Mon, 30 Jan 2023 21:21:48 +0100
Subject: [PATCH] bpf: fix restrict_fs on s390x
Linux kernel's bpf-next contains BPF LSM support for s390x. systemd's
test-bpf-lsm currently fails with this kernel.
This is an endianness issue: in the restrict_fs bpf program,
magic_number has type unsigned long (64 bits on s390x), but magic_map
keys are uint32_t (32 bits). Accessing magic_map using 64-bit keys may
work by accident on little-endian systems, but fails hard on big-endian
ones.
Fix by casting magic_number to uint32_t.
(cherry picked from commit 907046282c27ee2ced5e22abb80ed8df2e157baf)
Resolves: #2230364
---
src/core/bpf/restrict_fs/restrict-fs.bpf.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/src/core/bpf/restrict_fs/restrict-fs.bpf.c b/src/core/bpf/restrict_fs/restrict-fs.bpf.c
index 522a029785..eb5ed3e7fe 100644
--- a/src/core/bpf/restrict_fs/restrict-fs.bpf.c
+++ b/src/core/bpf/restrict_fs/restrict-fs.bpf.c
@@ -39,16 +39,20 @@ struct {
SEC("lsm/file_open")
int BPF_PROG(restrict_filesystems, struct file *file, int ret)
{
- unsigned long magic_number;
+ unsigned long raw_magic_number;
uint64_t cgroup_id;
- uint32_t *value, *magic_map, zero = 0, *is_allow;
+ uint32_t *value, *magic_map, magic_number, zero = 0, *is_allow;
/* ret is the return value from the previous BPF program or 0 if it's
* the first hook */
if (ret != 0)
return ret;
- BPF_CORE_READ_INTO(&magic_number, file, f_inode, i_sb, s_magic);
+ BPF_CORE_READ_INTO(&raw_magic_number, file, f_inode, i_sb, s_magic);
+ /* super_block.s_magic is unsigned long, but magic_map keys are
+ * uint32_t. Using s_magic as-is would fail on big-endian systems,
+ * which have 64-bit unsigned long. So cast it. */
+ magic_number = (uint32_t)raw_magic_number;
cgroup_id = bpf_get_current_cgroup_id();