linux.git/kernel/bpf/bpf_struct_ops.c, branch v6.6.131 Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git bpf: Support default .validate() and .update() behavior for struct_ops links 2023-08-15T05:23:39+00:00 David Vernet void@manifault.com 2023-08-14T18:59:07+00:00 8ba651ed7fa1641f7c4941b79f2e3dd4ddb58aec Currently, if a struct_ops map is loaded with BPF_F_LINK, it must also define the .validate() and .update() callbacks in its corresponding struct bpf_struct_ops in the kernel. Enabling struct_ops link is useful in its own right to ensure that the map is unloaded if an application crashes. For example, with sched_ext, we want to automatically unload the host-wide scheduler if the application crashes. We would likely never support updating elements of a sched_ext struct_ops map, so we'd have to implement these callbacks showing that they _can't_ support element updates just to benefit from the basic lifetime management of struct_ops links. Let's enable struct_ops maps to work with BPF_F_LINK even if they haven't defined these callbacks, by assuming that a struct_ops map element cannot be updated by default. Acked-by: Kui-Feng Lee <thinker.li@gmail.com> Signed-off-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230814185908.700553-2-void@manifault.com Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> 
Currently, if a struct_ops map is loaded with BPF_F_LINK, it must also
define the .validate() and .update() callbacks in its corresponding
struct bpf_struct_ops in the kernel. Enabling struct_ops link is useful
in its own right to ensure that the map is unloaded if an application
crashes. For example, with sched_ext, we want to automatically unload
the host-wide scheduler if the application crashes. We would likely
never support updating elements of a sched_ext struct_ops map, so we'd
have to implement these callbacks showing that they _can't_ support
element updates just to benefit from the basic lifetime management of
struct_ops links.

Let's enable struct_ops maps to work with BPF_F_LINK even if they
haven't defined these callbacks, by assuming that a struct_ops map
element cannot be updated by default.

Acked-by: Kui-Feng Lee <thinker.li@gmail.com>
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230814185908.700553-2-void@manifault.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
bpf: bpf_struct_ops: Remove unnecessary initial values of variables 2023-08-04T00:54:35+00:00 Li kunyu kunyu@nfschina.com 2023-08-04T17:59:29+00:00 5964d1e4594eb1dbfc1e2a34ec89eb48f6b03e75 err and tlinks is assigned first, so it does not need to initialize the assignment. Signed-off-by: Li kunyu <kunyu@nfschina.com> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://lore.kernel.org/r/20230804175929.2867-1-kunyu@nfschina.com Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> 
err and tlinks is assigned first, so it does not need to initialize the
assignment.

Signed-off-by: Li kunyu <kunyu@nfschina.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230804175929.2867-1-kunyu@nfschina.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
bpf: Centralize permissions checks for all BPF map types 2023-06-19T12:04:04+00:00 Andrii Nakryiko andrii@kernel.org 2023-06-13T22:35:32+00:00 6c3eba1c5e283fd2bb1c076dbfcb47f569c3bfde This allows to do more centralized decisions later on, and generally makes it very explicit which maps are privileged and which are not (e.g., LRU_HASH and LRU_PERCPU_HASH, which are privileged HASH variants, as opposed to unprivileged HASH and HASH_PERCPU; now this is explicit and easy to verify). Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Stanislav Fomichev <sdf@google.com> Link: https://lore.kernel.org/bpf/20230613223533.3689589-4-andrii@kernel.org 
This allows to do more centralized decisions later on, and generally
makes it very explicit which maps are privileged and which are not
(e.g., LRU_HASH and LRU_PERCPU_HASH, which are privileged HASH variants,
as opposed to unprivileged HASH and HASH_PERCPU; now this is explicit
and easy to verify).

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20230613223533.3689589-4-andrii@kernel.org
bpf: Check IS_ERR for the bpf_map_get() return value 2023-03-24T19:40:47+00:00 Martin KaFai Lau martin.lau@kernel.org 2023-03-24T18:42:41+00:00 55fbae05476df65e5eee8be54f61d0257af0240b This patch fixes a mistake in checking NULL instead of checking IS_ERR for the bpf_map_get() return value. It also fixes the return value in link_update_map() from -EINVAL to PTR_ERR(*_map). Reported-by: syzbot+71ccc0fe37abb458406b@syzkaller.appspotmail.com Fixes: 68b04864ca42 ("bpf: Create links for BPF struct_ops maps.") Fixes: aef56f2e918b ("bpf: Update the struct_ops of a bpf_link.") Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Acked-by: Kui-Feng Lee <kuifeng@meta.com> Acked-by: Stanislav Fomichev <sdf@google.com> Link: https://lore.kernel.org/r/20230324184241.1387437-1-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
This patch fixes a mistake in checking NULL instead of
checking IS_ERR for the bpf_map_get() return value.

It also fixes the return value in link_update_map() from -EINVAL
to PTR_ERR(*_map).

Reported-by: syzbot+71ccc0fe37abb458406b@syzkaller.appspotmail.com
Fixes: 68b04864ca42 ("bpf: Create links for BPF struct_ops maps.")
Fixes: aef56f2e918b ("bpf: Update the struct_ops of a bpf_link.")
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Acked-by: Kui-Feng Lee <kuifeng@meta.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20230324184241.1387437-1-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf: Update the struct_ops of a bpf_link. 2023-03-23T05:53:02+00:00 Kui-Feng Lee kuifeng@meta.com 2023-03-23T03:24:02+00:00 aef56f2e918bf8fc8de25f0b36e8c2aba44116ec By improving the BPF_LINK_UPDATE command of bpf(), it should allow you to conveniently switch between different struct_ops on a single bpf_link. This would enable smoother transitions from one struct_ops to another. The struct_ops maps passing along with BPF_LINK_UPDATE should have the BPF_F_LINK flag. Signed-off-by: Kui-Feng Lee <kuifeng@meta.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230323032405.3735486-6-kuifeng@meta.com Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> 
By improving the BPF_LINK_UPDATE command of bpf(), it should allow you
to conveniently switch between different struct_ops on a single
bpf_link. This would enable smoother transitions from one struct_ops
to another.

The struct_ops maps passing along with BPF_LINK_UPDATE should have the
BPF_F_LINK flag.

Signed-off-by: Kui-Feng Lee <kuifeng@meta.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230323032405.3735486-6-kuifeng@meta.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
bpf: Create links for BPF struct_ops maps. 2023-03-23T05:53:02+00:00 Kui-Feng Lee kuifeng@meta.com 2023-03-23T03:24:00+00:00 68b04864ca425d1894c96b8141d4fba1181f11cb Make bpf_link support struct_ops. Previously, struct_ops were always used alone without any associated links. Upon updating its value, a struct_ops would be activated automatically. Yet other BPF program types required to make a bpf_link with their instances before they could become active. Now, however, you can create an inactive struct_ops, and create a link to activate it later. With bpf_links, struct_ops has a behavior similar to other BPF program types. You can pin/unpin them from their links and the struct_ops will be deactivated when its link is removed while previously need someone to delete the value for it to be deactivated. bpf_links are responsible for registering their associated struct_ops. You can only use a struct_ops that has the BPF_F_LINK flag set to create a bpf_link, while a structs without this flag behaves in the same manner as before and is registered upon updating its value. The BPF_LINK_TYPE_STRUCT_OPS serves a dual purpose. Not only is it used to craft the links for BPF struct_ops programs, but also to create links for BPF struct_ops them-self. Since the links of BPF struct_ops programs are only used to create trampolines internally, they are never seen in other contexts. Thus, they can be reused for struct_ops themself. To maintain a reference to the map supporting this link, we add bpf_struct_ops_link as an additional type. The pointer of the map is RCU and won't be necessary until later in the patchset. Signed-off-by: Kui-Feng Lee <kuifeng@meta.com> Link: https://lore.kernel.org/r/20230323032405.3735486-4-kuifeng@meta.com Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> 
Make bpf_link support struct_ops.  Previously, struct_ops were always
used alone without any associated links. Upon updating its value, a
struct_ops would be activated automatically. Yet other BPF program
types required to make a bpf_link with their instances before they
could become active. Now, however, you can create an inactive
struct_ops, and create a link to activate it later.

With bpf_links, struct_ops has a behavior similar to other BPF program
types. You can pin/unpin them from their links and the struct_ops will
be deactivated when its link is removed while previously need someone
to delete the value for it to be deactivated.

bpf_links are responsible for registering their associated
struct_ops. You can only use a struct_ops that has the BPF_F_LINK flag
set to create a bpf_link, while a structs without this flag behaves in
the same manner as before and is registered upon updating its value.

The BPF_LINK_TYPE_STRUCT_OPS serves a dual purpose. Not only is it
used to craft the links for BPF struct_ops programs, but also to
create links for BPF struct_ops them-self.  Since the links of BPF
struct_ops programs are only used to create trampolines internally,
they are never seen in other contexts. Thus, they can be reused for
struct_ops themself.

To maintain a reference to the map supporting this link, we add
bpf_struct_ops_link as an additional type. The pointer of the map is
RCU and won't be necessary until later in the patchset.

Signed-off-by: Kui-Feng Lee <kuifeng@meta.com>
Link: https://lore.kernel.org/r/20230323032405.3735486-4-kuifeng@meta.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
bpf: Retire the struct_ops map kvalue->refcnt. 2023-03-23T05:51:47+00:00 Kui-Feng Lee kuifeng@meta.com 2023-03-23T03:23:58+00:00 b671c2067a04c0668df174ff5dfdb573d1f9b074 We have replaced kvalue-refcnt with synchronize_rcu() to wait for an RCU grace period. Maintenance of kvalue->refcnt was a complicated task, as we had to simultaneously keep track of two reference counts: one for the reference count of bpf_map. When the kvalue->refcnt reaches zero, we also have to reduce the reference count on bpf_map - yet these steps are not performed in an atomic manner and require us to be vigilant when managing them. By eliminating kvalue->refcnt, we can make our maintenance more straightforward as the refcount of bpf_map is now solely managed! To prevent the trampoline image of a struct_ops from being released while it is still in use, we wait for an RCU grace period. The setsockopt(TCP_CONGESTION, "...") command allows you to change your socket's congestion control algorithm and can result in releasing the old struct_ops implementation. It is fine. However, this function is exposed through bpf_setsockopt(), it may be accessed by BPF programs as well. To ensure that the trampoline image belonging to struct_op can be safely called while its method is in use, the trampoline safeguarde the BPF program with rcu_read_lock(). Doing so prevents any destruction of the associated images before returning from a trampoline and requires us to wait for an RCU grace period. Signed-off-by: Kui-Feng Lee <kuifeng@meta.com> Link: https://lore.kernel.org/r/20230323032405.3735486-2-kuifeng@meta.com Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> 
We have replaced kvalue-refcnt with synchronize_rcu() to wait for an
RCU grace period.

Maintenance of kvalue->refcnt was a complicated task, as we had to
simultaneously keep track of two reference counts: one for the
reference count of bpf_map. When the kvalue->refcnt reaches zero, we
also have to reduce the reference count on bpf_map - yet these steps
are not performed in an atomic manner and require us to be vigilant
when managing them. By eliminating kvalue->refcnt, we can make our
maintenance more straightforward as the refcount of bpf_map is now
solely managed!

To prevent the trampoline image of a struct_ops from being released
while it is still in use, we wait for an RCU grace period. The
setsockopt(TCP_CONGESTION, "...") command allows you to change your
socket's congestion control algorithm and can result in releasing the
old struct_ops implementation. It is fine. However, this function is
exposed through bpf_setsockopt(), it may be accessed by BPF programs
as well. To ensure that the trampoline image belonging to struct_op
can be safely called while its method is in use, the trampoline
safeguarde the BPF program with rcu_read_lock(). Doing so prevents any
destruction of the associated images before returning from a
trampoline and requires us to wait for an RCU grace period.

Signed-off-by: Kui-Feng Lee <kuifeng@meta.com>
Link: https://lore.kernel.org/r/20230323032405.3735486-2-kuifeng@meta.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
bpf: return long from bpf_map_ops funcs 2023-03-22T22:11:30+00:00 JP Kobryn inwardvessel@gmail.com 2023-03-22T19:47:54+00:00 d7ba4cc900bf1eea2d8c807c6b1fc6bd61f41237 This patch changes the return types of bpf_map_ops functions to long, where previously int was returned. Using long allows for bpf programs to maintain the sign bit in the absence of sign extension during situations where inlined bpf helper funcs make calls to the bpf_map_ops funcs and a negative error is returned. The definitions of the helper funcs are generated from comments in the bpf uapi header at `include/uapi/linux/bpf.h`. The return type of these helpers was previously changed from int to long in commit bdb7b79b4ce8. For any case where one of the map helpers call the bpf_map_ops funcs that are still returning 32-bit int, a compiler might not include sign extension instructions to properly convert the 32-bit negative value a 64-bit negative value. For example: bpf assembly excerpt of an inlined helper calling a kernel function and checking for a specific error: ; err = bpf_map_update_elem(&mymap, &key, &val, BPF_NOEXIST); ... 46: call 0xffffffffe103291c ; htab_map_update_elem ; if (err && err != -EEXIST) { 4b: cmp $0xffffffffffffffef,%rax ; cmp -EEXIST,%rax kernel function assembly excerpt of return value from `htab_map_update_elem` returning 32-bit int: movl $0xffffffef, %r9d ... movl %r9d, %eax ...results in the comparison: cmp $0xffffffffffffffef, $0x00000000ffffffef Fixes: bdb7b79b4ce8 ("bpf: Switch most helper return values from 32-bit int to 64-bit long") Tested-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: JP Kobryn <inwardvessel@gmail.com> Link: https://lore.kernel.org/r/20230322194754.185781-3-inwardvessel@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
This patch changes the return types of bpf_map_ops functions to long, where
previously int was returned. Using long allows for bpf programs to maintain
the sign bit in the absence of sign extension during situations where
inlined bpf helper funcs make calls to the bpf_map_ops funcs and a negative
error is returned.

The definitions of the helper funcs are generated from comments in the bpf
uapi header at `include/uapi/linux/bpf.h`. The return type of these
helpers was previously changed from int to long in commit bdb7b79b4ce8. For
any case where one of the map helpers call the bpf_map_ops funcs that are
still returning 32-bit int, a compiler might not include sign extension
instructions to properly convert the 32-bit negative value a 64-bit
negative value.

For example:
bpf assembly excerpt of an inlined helper calling a kernel function and
checking for a specific error:

; err = bpf_map_update_elem(&mymap, &key, &val, BPF_NOEXIST);
  ...
  46:	call   0xffffffffe103291c	; htab_map_update_elem
; if (err && err != -EEXIST) {
  4b:	cmp    $0xffffffffffffffef,%rax ; cmp -EEXIST,%rax

kernel function assembly excerpt of return value from
`htab_map_update_elem` returning 32-bit int:

movl $0xffffffef, %r9d
...
movl %r9d, %eax

...results in the comparison:
cmp $0xffffffffffffffef, $0x00000000ffffffef

Fixes: bdb7b79b4ce8 ("bpf: Switch most helper return values from 32-bit int to 64-bit long")
Tested-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
Link: https://lore.kernel.org/r/20230322194754.185781-3-inwardvessel@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf: bpf_struct_ops memory usage 2023-03-07T17:33:43+00:00 Yafang Shao laoar.shao@gmail.com 2023-03-05T12:46:09+00:00 f062226d8d59b521ddc946ad791048188a16722a A new helper is introduced to calculate bpf_struct_ops memory usage. The result as follows, - before 1: struct_ops name count_map flags 0x0 key 4B value 256B max_entries 1 memlock 4096B btf_id 73 - after 1: struct_ops name count_map flags 0x0 key 4B value 256B max_entries 1 memlock 5016B btf_id 73 Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Link: https://lore.kernel.org/r/20230305124615.12358-13-laoar.shao@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
A new helper is introduced to calculate bpf_struct_ops memory usage.

The result as follows,

- before
1: struct_ops  name count_map  flags 0x0
        key 4B  value 256B  max_entries 1  memlock 4096B
        btf_id 73

- after
1: struct_ops  name count_map  flags 0x0
        key 4B  value 256B  max_entries 1  memlock 5016B
        btf_id 73

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20230305124615.12358-13-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
mm: Introduce set_memory_rox() 2022-12-15T18:37:26+00:00 Peter Zijlstra peterz@infradead.org 2022-10-26T10:13:03+00:00 d48567c9a0d1e605639f8a8705a61bbb55fb4e84 Because endlessly repeating: set_memory_ro() set_memory_x() is getting tedious. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/Y1jek64pXOsougmz@hirez.programming.kicks-ass.net 
Because endlessly repeating:

	set_memory_ro()
	set_memory_x()

is getting tedious.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/Y1jek64pXOsougmz@hirez.programming.kicks-ass.net