Pull x86 spectre fixes from Borislav Petkov: - Mitigate Spectre v2-type Branch History Buffer attacks on machines which support eIBRS, i.e., the hardware-assisted speculation restriction after it has been shown that such machines are vulnerable even with the hardware mitigation. - Do not use the default LFENCE-based Spectre v2 mitigation on AMD as it is insufficient to mitigate such attacks. Instead, switch to retpolines on all AMD by default. - Update the docs and add some warnings for the obviously vulnerable cmdline configurations. * tag 'x86_bugs_for_v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/speculation: Warn about eIBRS + LFENCE + Unprivileged eBPF + SMT x86/speculation: Warn about Spectre v2 LFENCE mitigation x86/speculation: Update link to AMD speculation whitepaper x86/speculation: Use generic retpoline by default on AMD x86/speculation: Include unprivileged eBPF status in Spectre v2 mitigation reporting Documentation/hw-vuln: Update spectre doc x86/speculation: Add eIBRS + Retpoline options x86/speculation: Rename RETPOLINE_AMD to RETPOLINE_LFENCE
With unprivileged eBPF enabled, eIBRS (without retpoline) is vulnerable to Spectre v2 BHB-based attacks. When both are enabled, print a warning message and report it in the 'spectre_v2' sysfs vulnerabilities file. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
The patch in [1] intends to fix a bpf_timer related issue,
but the fix caused existing 'timer' selftest to fail with
hang or some random errors. After some debug, I found
an issue with check_and_init_map_value() in the hashtab.c.
More specifically, in hashtab.c, we have code
l_new = bpf_map_kmalloc_node(&htab->map, ...)
check_and_init_map_value(&htab->map, l_new...)
Note that bpf_map_kmalloc_node() does not do initialization
so l_new contains random value.
The function check_and_init_map_value() intends to zero the
bpf_spin_lock and bpf_timer if they exist in the map.
But I found bpf_spin_lock is zero'ed but bpf_timer is not zero'ed.
With [1], later copy_map_value() skips copying of
bpf_spin_lock and bpf_timer. The non-zero bpf_timer caused
random failures for 'timer' selftest.
Without [1], for both bpf_spin_lock and bpf_timer case,
bpf_timer will be zero'ed, so 'timer' self test is okay.
For check_and_init_map_value(), why bpf_spin_lock is zero'ed
properly while bpf_timer not. In bpf uapi header, we have
struct bpf_spin_lock {
__u32 val;
};
struct bpf_timer {
__u64 :64;
__u64 :64;
} __attribute__((aligned(8)));
The initialization code:
*(struct bpf_spin_lock *)(dst + map->spin_lock_off) =
(struct bpf_spin_lock){};
*(struct bpf_timer *)(dst + map->timer_off) =
(struct bpf_timer){};
It appears the compiler has no obligation to initialize anonymous fields.
For example, let us use clang with bpf target as below:
$ cat t.c
struct bpf_timer {
unsigned long long :64;
};
struct bpf_timer2 {
unsigned long long a;
};
void test(struct bpf_timer *t) {
*t = (struct bpf_timer){};
}
void test2(struct bpf_timer2 *t) {
*t = (struct bpf_timer2){};
}
$ clang -target bpf -O2 -c -g t.c
$ llvm-objdump -d t.o
...
0000000000000000 <test>:
0: 95 00 00 00 00 00 00 00 exit
0000000000000008 <test2>:
1: b7 02 00 00 00 00 00 00 r2 = 0
2: 7b 21 00 00 00 00 00 00 *(u64 *)(r1 + 0) = r2
3: 95 00 00 00 00 00 00 00 exit
gcc11.2 does not have the above issue. But from
INTERNATIONAL STANDARD ©ISO/IEC ISO/IEC 9899:201x
Programming languages — C
http://www.open-std.org/Jtc1/sc22/wg14/www/docs/n1547.pdf
page 157:
Except where explicitly stated otherwise, for the purposes of
this subclause unnamed members of objects of structure and union
type do not participate in initialization. Unnamed members of
structure objects have indeterminate value even after initialization.
To fix the problem, let use memset for bpf_timer case in
check_and_init_map_value(). For consistency, memset is also
used for bpf_spin_lock case.
[1] https://lore.kernel.org/bpf/20220209070324.1093182-2-memxor@gmail.com/
Fixes: 68134668c17f3 ("bpf: Add map side support for bpf timers.")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220211194953.3142152-1-yhs@fb.com
When both bpf_spin_lock and bpf_timer are present in a BPF map value,
copy_map_value needs to skirt both objects when copying a value into and
out of the map. However, the current code does not set both s_off and
t_off in copy_map_value, which leads to a crash when e.g. bpf_spin_lock
is placed in map value with bpf_timer, as bpf_map_update_elem call will
be able to overwrite the other timer object.
When the issue is not fixed, an overwriting can produce the following
splat:
[root@(none) bpf]# ./test_progs -t timer_crash
[ 15.930339] bpf_testmod: loading out-of-tree module taints kernel.
[ 16.037849] ==================================================================
[ 16.038458] BUG: KASAN: user-memory-access in __pv_queued_spin_lock_slowpath+0x32b/0x520
[ 16.038944] Write of size 8 at addr 0000000000043ec0 by task test_progs/325
[ 16.039399]
[ 16.039514] CPU: 0 PID: 325 Comm: test_progs Tainted: G OE 5.16.0+ #278
[ 16.039983] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ArchLinux 1.15.0-1 04/01/2014
[ 16.040485] Call Trace:
[ 16.040645] <TASK>
[ 16.040805] dump_stack_lvl+0x59/0x73
[ 16.041069] ? __pv_queued_spin_lock_slowpath+0x32b/0x520
[ 16.041427] kasan_report.cold+0x116/0x11b
[ 16.041673] ? __pv_queued_spin_lock_slowpath+0x32b/0x520
[ 16.042040] __pv_queued_spin_lock_slowpath+0x32b/0x520
[ 16.042328] ? memcpy+0x39/0x60
[ 16.042552] ? pv_hash+0xd0/0xd0
[ 16.042785] ? lockdep_hardirqs_off+0x95/0xd0
[ 16.043079] __bpf_spin_lock_irqsave+0xdf/0xf0
[ 16.043366] ? bpf_get_current_comm+0x50/0x50
[ 16.043608] ? jhash+0x11a/0x270
[ 16.043848] bpf_timer_cancel+0x34/0xe0
[ 16.044119] bpf_prog_c4ea1c0f7449940d_sys_enter+0x7c/0x81
[ 16.044500] bpf_trampoline_6442477838_0+0x36/0x1000
[ 16.044836] __x64_sys_nanosleep+0x5/0x140
[ 16.045119] do_syscall_64+0x59/0x80
[ 16.045377] ? lock_is_held_type+0xe4/0x140
[ 16.045670] ? irqentry_exit_to_user_mode+0xa/0x40
[ 16.046001] ? mark_held_locks+0x24/0x90
[ 16.046287] ? asm_exc_page_fault+0x1e/0x30
[ 16.046569] ? asm_exc_page_fault+0x8/0x30
[ 16.046851] ? lockdep_hardirqs_on+0x7e/0x100
[ 16.047137] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 16.047405] RIP: 0033:0x7f9e4831718d
[ 16.047602] Code: b4 0c 00 0f 05 eb a9 66 0f 1f 44 00 00 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d b3 6c 0c 00 f7 d8 64 89 01 48
[ 16.048764] RSP: 002b:00007fff488086b8 EFLAGS: 00000206 ORIG_RAX: 0000000000000023
[ 16.049275] RAX: ffffffffffffffda RBX: 00007f9e48683740 RCX: 00007f9e4831718d
[ 16.049747] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007fff488086d0
[ 16.050225] RBP: 00007fff488086f0 R08: 00007fff488085d7 R09: 00007f9e4cb594a0
[ 16.050648] R10: 0000000000000000 R11: 0000000000000206 R12: 00007f9e484cde30
[ 16.051124] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[ 16.051608] </TASK>
[ 16.051762] ==================================================================
Fixes: 68134668c17f ("bpf: Add map side support for bpf timers.")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220209070324.1093182-2-memxor@gmail.com
The bpf_ringbuf_submit() and bpf_ringbuf_discard() have ARG_PTR_TO_ALLOC_MEM
in their bpf_func_proto definition as their first argument, and thus both expect
the result from a prior bpf_ringbuf_reserve() call which has a return type of
RET_PTR_TO_ALLOC_MEM_OR_NULL.
While the non-NULL memory from bpf_ringbuf_reserve() can be passed to other
helpers, the two sinks (bpf_ringbuf_submit(), bpf_ringbuf_discard()) right now
only enforce a register type of PTR_TO_MEM.
This can lead to potential type confusion since it would allow other PTR_TO_MEM
memory to be passed into the two sinks which did not come from bpf_ringbuf_reserve().
Add a new MEM_ALLOC composable type attribute for PTR_TO_MEM, and enforce that:
- bpf_ringbuf_reserve() returns NULL or PTR_TO_MEM | MEM_ALLOC
- bpf_ringbuf_submit() and bpf_ringbuf_discard() only take PTR_TO_MEM | MEM_ALLOC
but not plain PTR_TO_MEM arguments via ARG_PTR_TO_ALLOC_MEM
- however, other helpers might treat PTR_TO_MEM | MEM_ALLOC as plain PTR_TO_MEM
to populate the memory area when they use ARG_PTR_TO_{UNINIT_,}MEM in their
func proto description
Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it")
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
All map redirect functions except XSK maps convert xdp_buff to xdp_frame before enqueueing it. So move this conversion of out the map functions and into xdp_do_redirect(). This removes a bit of duplicated code, but more importantly it makes it possible to support caller-allocated xdp_frame structures, which will be added in a subsequent commit. Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220103150812.87914-5-toke@redhat.com
Some helper functions may modify its arguments, for example, bpf_d_path, bpf_get_stack etc. Previously, their argument types were marked as ARG_PTR_TO_MEM, which is compatible with read-only mem types, such as PTR_TO_RDONLY_BUF. Therefore it's legitimate, but technically incorrect, to modify a read-only memory by passing it into one of such helper functions. This patch tags the bpf_args compatible with immutable memory with MEM_RDONLY flag. The arguments that don't have this flag will be only compatible with mutable memory types, preventing the helper from modifying a read-only memory. The bpf_args that have MEM_RDONLY are compatible with both mutable memory and immutable memory. Signed-off-by: Hao Luo <haoluo@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211217003152.48334-9-haoluo@google.com
Remove PTR_TO_MEM_OR_NULL and replace it with PTR_TO_MEM combined with flag PTR_MAYBE_NULL. Signed-off-by: Hao Luo <haoluo@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211217003152.48334-7-haoluo@google.com
This patch introduce a flag MEM_RDONLY to tag a reg value pointing to read-only memory. It makes the following changes: 1. PTR_TO_RDWR_BUF -> PTR_TO_BUF 2. PTR_TO_RDONLY_BUF -> PTR_TO_BUF | MEM_RDONLY Signed-off-by: Hao Luo <haoluo@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211217003152.48334-6-haoluo@google.com
We have introduced a new type to make bpf_reg composable, by allocating bits in the type to represent flags. One of the flags is PTR_MAYBE_NULL which indicates a pointer may be NULL. This patch switches the qualified reg_types to use this flag. The reg_types changed in this patch include: 1. PTR_TO_MAP_VALUE_OR_NULL 2. PTR_TO_SOCKET_OR_NULL 3. PTR_TO_SOCK_COMMON_OR_NULL 4. PTR_TO_TCP_SOCK_OR_NULL 5. PTR_TO_BTF_ID_OR_NULL 6. PTR_TO_MEM_OR_NULL 7. PTR_TO_RDONLY_BUF_OR_NULL 8. PTR_TO_RDWR_BUF_OR_NULL Signed-off-by: Hao Luo <haoluo@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/r/20211217003152.48334-5-haoluo@google.com