This series is a follow-up to [0]. patch 1 updates sk_storage_map_test to ensure special map value fields are not copied between user and kernel. patch 0 fixes a bug found by the updated test.
[0] https://lore.kernel.org/bpf/1ca2e4e8-ed7e-9174-01f6-c14539b8b8b2@huawei.com/
Xu Kuohai (2): bpf: Do not copy spin lock field from user in bpf_selem_alloc bpf: Set and check spin lock value in sk_storage_map_test
kernel/bpf/bpf_local_storage.c | 2 +- .../selftests/bpf/map_tests/sk_storage_map.c | 36 ++++++++++--------- 2 files changed, 21 insertions(+), 17 deletions(-)
bpf_selem_alloc function is used by inode_storage, sk_storage and task_storage maps to set map value, for these map types, there may be a spin lock in the map value, so if we use memcpy to copy the whole map value from user, the spin lock field may be initialized incorrectly.
Since the spin lock field is zeroed by kzalloc, call copy_map_value instead of memcpy to skip copying the spin lock field to fix it.
Fixes: 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage") Signed-off-by: Xu Kuohai xukuohai@huawei.com --- kernel/bpf/bpf_local_storage.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index 802fc15b0d73..f27fa5ba7d72 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -74,7 +74,7 @@ bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner, gfp_flags | __GFP_NOWARN); if (selem) { if (value) - memcpy(SDATA(selem)->data, value, smap->map.value_size); + copy_map_value(&smap->map, SDATA(selem)->data, value); return selem; }
On Mon, Nov 14, 2022 at 5:31 AM Xu Kuohai xukuohai@huawei.com wrote:
bpf_selem_alloc function is used by inode_storage, sk_storage and task_storage maps to set map value, for these map types, there may be a spin lock in the map value, so if we use memcpy to copy the whole map value from user, the spin lock field may be initialized incorrectly.
Since the spin lock field is zeroed by kzalloc, call copy_map_value instead of memcpy to skip copying the spin lock field to fix it.
Fixes: 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage")
The tag is wrong. When local storage was introduced it was not possible to use spin_locks there. Pls resubmit.
On 11/16/2022 1:27 PM, Alexei Starovoitov wrote:
On Mon, Nov 14, 2022 at 5:31 AM Xu Kuohai xukuohai@huawei.com wrote:
bpf_selem_alloc function is used by inode_storage, sk_storage and task_storage maps to set map value, for these map types, there may be a spin lock in the map value, so if we use memcpy to copy the whole map value from user, the spin lock field may be initialized incorrectly.
Since the spin lock field is zeroed by kzalloc, call copy_map_value instead of memcpy to skip copying the spin lock field to fix it.
Fixes: 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage")
The tag is wrong. When local storage was introduced it was not possible to use spin_locks there. Pls resubmit. .
No, spin_lock was introduced by d83525ca62cf ("bpf: introduce bpf_spin_lock"), before 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage").
To confirm this, I built a kernel image on comit 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage") and run test case posted in patch 2, a softlockup was triggered. Then I picked this patch and tried again, nothing failed.
On 11/16/2022 4:07 PM, Xu Kuohai wrote:
On 11/16/2022 1:27 PM, Alexei Starovoitov wrote:
On Mon, Nov 14, 2022 at 5:31 AM Xu Kuohai xukuohai@huawei.com wrote:
bpf_selem_alloc function is used by inode_storage, sk_storage and task_storage maps to set map value, for these map types, there may be a spin lock in the map value, so if we use memcpy to copy the whole map value from user, the spin lock field may be initialized incorrectly.
Since the spin lock field is zeroed by kzalloc, call copy_map_value instead of memcpy to skip copying the spin lock field to fix it.
Fixes: 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage")
The tag is wrong. When local storage was introduced it was not possible to use spin_locks there. Pls resubmit. .
No, spin_lock was introduced by d83525ca62cf ("bpf: introduce bpf_spin_lock"), before 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage").
To confirm this, I built a kernel image on comit 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage") and run test case posted in patch 2, a softlockup was triggered. Then I picked this patch and tried again, nothing failed.
Hello, am I right? Or could you please give the correct fix-tag? Thanks.
On Mon, Nov 21, 2022 at 3:30 AM Xu Kuohai xukuohai@huaweicloud.com wrote:
On 11/16/2022 4:07 PM, Xu Kuohai wrote:
On 11/16/2022 1:27 PM, Alexei Starovoitov wrote:
On Mon, Nov 14, 2022 at 5:31 AM Xu Kuohai xukuohai@huawei.com wrote:
bpf_selem_alloc function is used by inode_storage, sk_storage and task_storage maps to set map value, for these map types, there may be a spin lock in the map value, so if we use memcpy to copy the whole map value from user, the spin lock field may be initialized incorrectly.
Since the spin lock field is zeroed by kzalloc, call copy_map_value instead of memcpy to skip copying the spin lock field to fix it.
Fixes: 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage")
The tag is wrong. When local storage was introduced it was not possible to use spin_locks there. Pls resubmit. .
No, spin_lock was introduced by d83525ca62cf ("bpf: introduce bpf_spin_lock"), before 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage").
To confirm this, I built a kernel image on comit 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage") and run test case posted in patch 2, a softlockup was triggered. Then I picked this patch and tried again, nothing failed.
Hello, am I right? Or could you please give the correct fix-tag? Thanks.
I see. I was under the impression that bpf_spin_lock was enabled in the local storage later. Ok. Applied as-is.
Update sk_storage_map_test to make sure kernel does not copy user non-zero value spin lock to kernel, and does not copy kernel spin lock value to user.
If user spin lock value is copied to kernel, this test case will make kernel spin on the copied lock, resulting in rcu stall and softlockup.
Signed-off-by: Xu Kuohai xukuohai@huawei.com --- .../selftests/bpf/map_tests/sk_storage_map.c | 36 ++++++++++--------- 1 file changed, 20 insertions(+), 16 deletions(-)
diff --git a/tools/testing/selftests/bpf/map_tests/sk_storage_map.c b/tools/testing/selftests/bpf/map_tests/sk_storage_map.c index 099eb4dfd4f7..18405c3b7cee 100644 --- a/tools/testing/selftests/bpf/map_tests/sk_storage_map.c +++ b/tools/testing/selftests/bpf/map_tests/sk_storage_map.c @@ -458,7 +458,7 @@ static void test_sk_storage_map_basic(void) struct { int cnt; int lock; - } value = { .cnt = 0xeB9f, .lock = 0, }, lookup_value; + } value = { .cnt = 0xeB9f, .lock = 1, }, lookup_value; struct bpf_map_create_opts bad_xattr; int btf_fd, map_fd, sk_fd, err;
@@ -483,38 +483,41 @@ static void test_sk_storage_map_basic(void) "err:%d errno:%d\n", err, errno); err = bpf_map_lookup_elem_flags(map_fd, &sk_fd, &lookup_value, BPF_F_LOCK); - CHECK(err || lookup_value.cnt != value.cnt, + CHECK(err || lookup_value.lock || lookup_value.cnt != value.cnt, "bpf_map_lookup_elem_flags(BPF_F_LOCK)", - "err:%d errno:%d cnt:%x(%x)\n", - err, errno, lookup_value.cnt, value.cnt); + "err:%d errno:%d lock:%x cnt:%x(%x)\n", + err, errno, lookup_value.lock, lookup_value.cnt, value.cnt);
/* Bump the cnt and update with BPF_EXIST | BPF_F_LOCK */ value.cnt += 1; + value.lock = 2; err = bpf_map_update_elem(map_fd, &sk_fd, &value, BPF_EXIST | BPF_F_LOCK); CHECK(err, "bpf_map_update_elem(BPF_EXIST|BPF_F_LOCK)", "err:%d errno:%d\n", err, errno); err = bpf_map_lookup_elem_flags(map_fd, &sk_fd, &lookup_value, BPF_F_LOCK); - CHECK(err || lookup_value.cnt != value.cnt, + CHECK(err || lookup_value.lock || lookup_value.cnt != value.cnt, "bpf_map_lookup_elem_flags(BPF_F_LOCK)", - "err:%d errno:%d cnt:%x(%x)\n", - err, errno, lookup_value.cnt, value.cnt); + "err:%d errno:%d lock:%x cnt:%x(%x)\n", + err, errno, lookup_value.lock, lookup_value.cnt, value.cnt);
/* Bump the cnt and update with BPF_EXIST */ value.cnt += 1; + value.lock = 2; err = bpf_map_update_elem(map_fd, &sk_fd, &value, BPF_EXIST); CHECK(err, "bpf_map_update_elem(BPF_EXIST)", "err:%d errno:%d\n", err, errno); err = bpf_map_lookup_elem_flags(map_fd, &sk_fd, &lookup_value, BPF_F_LOCK); - CHECK(err || lookup_value.cnt != value.cnt, + CHECK(err || lookup_value.lock || lookup_value.cnt != value.cnt, "bpf_map_lookup_elem_flags(BPF_F_LOCK)", - "err:%d errno:%d cnt:%x(%x)\n", - err, errno, lookup_value.cnt, value.cnt); + "err:%d errno:%d lock:%x cnt:%x(%x)\n", + err, errno, lookup_value.lock, lookup_value.cnt, value.cnt);
/* Update with BPF_NOEXIST */ value.cnt += 1; + value.lock = 2; err = bpf_map_update_elem(map_fd, &sk_fd, &value, BPF_NOEXIST | BPF_F_LOCK); CHECK(!err || errno != EEXIST, @@ -526,22 +529,23 @@ static void test_sk_storage_map_basic(void) value.cnt -= 1; err = bpf_map_lookup_elem_flags(map_fd, &sk_fd, &lookup_value, BPF_F_LOCK); - CHECK(err || lookup_value.cnt != value.cnt, + CHECK(err || lookup_value.lock || lookup_value.cnt != value.cnt, "bpf_map_lookup_elem_flags(BPF_F_LOCK)", - "err:%d errno:%d cnt:%x(%x)\n", - err, errno, lookup_value.cnt, value.cnt); + "err:%d errno:%d lock:%x cnt:%x(%x)\n", + err, errno, lookup_value.lock, lookup_value.cnt, value.cnt);
/* Bump the cnt again and update with map_flags == 0 */ value.cnt += 1; + value.lock = 2; err = bpf_map_update_elem(map_fd, &sk_fd, &value, 0); CHECK(err, "bpf_map_update_elem()", "err:%d errno:%d\n", err, errno); err = bpf_map_lookup_elem_flags(map_fd, &sk_fd, &lookup_value, BPF_F_LOCK); - CHECK(err || lookup_value.cnt != value.cnt, + CHECK(err || lookup_value.lock || lookup_value.cnt != value.cnt, "bpf_map_lookup_elem_flags(BPF_F_LOCK)", - "err:%d errno:%d cnt:%x(%x)\n", - err, errno, lookup_value.cnt, value.cnt); + "err:%d errno:%d lock:%x cnt:%x(%x)\n", + err, errno, lookup_value.lock, lookup_value.cnt, value.cnt);
/* Test delete elem */ err = bpf_map_delete_elem(map_fd, &sk_fd);
linux-kselftest-mirror@lists.linaro.org
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Alexei Starovoitov -
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Xu Kuohai