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