Lorenzo Bianconi <[email protected]> writes: >> Lorenzo Bianconi <[email protected]> writes: >> >> > In the current implementation if the program is dev-bound to a specific >> > device, it will not be possible to perform XDP_REDIRECT into a DEVMAP >> > or CPUMAP even if the program is running in the driver NAPI context and >> > it is not attached to any map entry. This seems in contrast with the >> > explanation available in bpf_prog_map_compatible routine. >> > Fix the issue introducing __bpf_prog_map_compatible utility routine in >> > order to avoid bpf_prog_is_dev_bound() check running bpf_check_tail_call() >> > at program load time (bpf_prog_select_runtime()). >> > Continue forbidding to attach a dev-bound program to XDP maps >> > (BPF_MAP_TYPE_PROG_ARRAY, BPF_MAP_TYPE_DEVMAP and BPF_MAP_TYPE_CPUMAP). >> > >> > Fixes: 3d76a4d3d4e59 ("bpf: XDP metadata RX kfuncs") >> > Signed-off-by: Lorenzo Bianconi <[email protected]> >> > --- >> > Changes in v2: >> > - Introduce __bpf_prog_map_compatible() utility routine in order to skip >> > bpf_prog_is_dev_bound check in bpf_check_tail_call() >> > - Extend xdp_metadata selftest >> > - Link to v1: >> > https://lore.kernel.org/r/[email protected] >> > --- >> > kernel/bpf/core.c | 27 >> > +++++++++++++--------- >> > .../selftests/bpf/prog_tests/xdp_metadata.c | 22 +++++++++++++++++- >> > tools/testing/selftests/bpf/progs/xdp_metadata.c | 13 +++++++++++ >> > 3 files changed, 50 insertions(+), 12 deletions(-) >> > >> > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c >> > index >> > ba6b6118cf504041278d05417c4212d57be6fca0..a3e571688421196c3ceaed62b3b59b62a0258a8c >> > 100644 >> > --- a/kernel/bpf/core.c >> > +++ b/kernel/bpf/core.c >> > @@ -2358,8 +2358,8 @@ static unsigned int __bpf_prog_ret0_warn(const void >> > *ctx, >> > return 0; >> > } >> > >> > -bool bpf_prog_map_compatible(struct bpf_map *map, >> > - const struct bpf_prog *fp) >> > +static bool __bpf_prog_map_compatible(struct bpf_map *map, >> > + const struct bpf_prog *fp) >> > { >> > enum bpf_prog_type prog_type = resolve_prog_type(fp); >> > bool ret; >> > @@ -2368,14 +2368,6 @@ bool bpf_prog_map_compatible(struct bpf_map *map, >> > if (fp->kprobe_override) >> > return false; >> > >> > - /* XDP programs inserted into maps are not guaranteed to run on >> > - * a particular netdev (and can run outside driver context entirely >> > - * in the case of devmap and cpumap). Until device checks >> > - * are implemented, prohibit adding dev-bound programs to program maps. >> > - */ >> > - if (bpf_prog_is_dev_bound(aux)) >> > - return false; >> > - >> > spin_lock(&map->owner.lock); >> > if (!map->owner.type) { >> > /* There's no owner yet where we could check for >> > @@ -2409,6 +2401,19 @@ bool bpf_prog_map_compatible(struct bpf_map *map, >> > return ret; >> > } >> > >> > +bool bpf_prog_map_compatible(struct bpf_map *map, const struct bpf_prog >> > *fp) >> > +{ >> > + /* XDP programs inserted into maps are not guaranteed to run on >> > + * a particular netdev (and can run outside driver context entirely >> > + * in the case of devmap and cpumap). Until device checks >> > + * are implemented, prohibit adding dev-bound programs to program maps. >> > + */ >> > + if (bpf_prog_is_dev_bound(fp->aux)) >> > + return false; >> > + >> > + return __bpf_prog_map_compatible(map, fp); >> > +} >> > + >> > static int bpf_check_tail_call(const struct bpf_prog *fp) >> > { >> > struct bpf_prog_aux *aux = fp->aux; >> > @@ -2421,7 +2426,7 @@ static int bpf_check_tail_call(const struct bpf_prog >> > *fp) >> > if (!map_type_contains_progs(map)) >> > continue; >> > >> > - if (!bpf_prog_map_compatible(map, fp)) { >> > + if (!__bpf_prog_map_compatible(map, fp)) { >> >> Hmm, so this allows devbound programs in tail call maps, right? But >> there's no guarantee that a tail call map will always be used for a >> particular device, is there? For instance, it could be shared between >> multiple XDP programs, bound to different devices, thus getting the >> wrong kfunc. > > According to my understanding the following path will be executed just for > dev-bound program that performs XDP_REDIRECT into a BPF_MAP_TYPE_PROG_ARRAY: > > bpf_prog_select_runtime() -> bpf_check_tail_call() -> > __bpf_prog_map_compatible() > > while for XDP program inserted into BPF_MAP_TYPE_PROG_ARRAY we will continue > running bpf_prog_map_compatible() so we will forbid inserting ev-bound > programs. > This is even tested into xdp_metadata selftest: > > https://github.com/torvalds/linux/blob/master/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c#L416 > > It seems to me v2 is not more relaxed than v1. Am I missing something?
No, you're right; see my reply to Stanislav - I misremembered the logic :) -Toke
