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. Or you could even have dev-bound programs tail-called from non-dev-bound programs with this change AFAICT? In other words, I think this is too relaxed, your change in v1 that only relaxed cpumap and devmap checks here was better. In fact, I don't really see why bpf_check_tail_call() needs to look at devmap/cpumap at all, so maybe just changing the map_type_contains_progs() call to only match tail call maps is better? -Toke
