Le 09/07/2024 à 11:15, Greg KH a écrit : > On Mon, Jul 08, 2024 at 03:12:55PM +0000, LEROY Christophe wrote: >> >> >> Le 08/07/2024 à 14:36, Greg KH a écrit : >>> On Sun, Jul 07, 2024 at 03:34:15PM +0800, WangYuli wrote: >>>> >>>> On 2024/7/6 17:30, Greg KH wrote: >>>>> This makes it sound like you are reverting this because of a build >>>>> error, which is not the case here, right? Isn't this because of the >>>>> powerpc issue reported here: >>>>> https://lore.kernel.org/r/20240705203413.wbv2nw3747vjeibk@xxxxxxxxxxxx >>>>> ? >>>> >>>> No, it only occurs on ARM64 architecture. The reason is that before being >>>> modified, the function >>>> >>>> bpf_jit_binary_lock_ro() in arch/arm64/net/bpf_jit_comp.c +1651 >>>> >>>> was introduced with __must_check, which is defined as >>>> __attribute__((__warn_unused_result__)). >>>> >>>> >>>> However, at this point, calling bpf_jit_binary_lock_ro(header) >>>> coincidentally results in an unused-result >>>> >>>> warning. >>> >>> Ok, thanks, but why is no one else seeing this in their testing? >> >> Probably the configs used by robots do not activate BPF JIT ? >> >>> >>>>> If not, why not just backport the single missing arm64 commit, >>>> >>>> Upstream commit 1dad391daef1 ("bpf, arm64: use bpf_prog_pack for memory >>>> management") is part of >>>> >>>> a larger change that involves multiple commits. It's not an isolated commit. >>>> >>>> >>>> We could certainly backport all of them to solve this problem, buthas it's not >>>> the simplest solution. >>> >>> reverting the change feels wrong in that you will still have the bug >>> present that it was trying to solve, right? If so, can you then provide >>> a working version? >> >> Indeed, by reverting the change you "punish" all architectures because >> arm64 hasn't properly been backported, is it fair ? >> >> In fact, when I implemented commit e60adf513275 ("bpf: Take return from >> set_memory_rox() into account with bpf_jit_binary_lock_ro()"), we had >> the following users for function bpf_jit_binary_lock_ro() : >> >> $ git grep bpf_jit_binary_lock_ro e60adf513275~ >> e60adf513275~:arch/arm/net/bpf_jit_32.c: >> bpf_jit_binary_lock_ro(header); >> e60adf513275~:arch/loongarch/net/bpf_jit.c: >> bpf_jit_binary_lock_ro(header); >> e60adf513275~:arch/mips/net/bpf_jit_comp.c: >> bpf_jit_binary_lock_ro(header); >> e60adf513275~:arch/parisc/net/bpf_jit_core.c: >> bpf_jit_binary_lock_ro(jit_data->header); >> e60adf513275~:arch/s390/net/bpf_jit_comp.c: >> bpf_jit_binary_lock_ro(header); >> e60adf513275~:arch/sparc/net/bpf_jit_comp_64.c: >> bpf_jit_binary_lock_ro(header); >> e60adf513275~:arch/x86/net/bpf_jit_comp32.c: >> bpf_jit_binary_lock_ro(header); >> e60adf513275~:include/linux/filter.h:static inline void >> bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr) >> >> But when commit 08f6c05feb1d ("bpf: Take return from set_memory_rox() >> into account with bpf_jit_binary_lock_ro()") was applied, we had one >> more user which is arm64: >> >> $ git grep bpf_jit_binary_lock_ro 08f6c05feb1d~ >> 08f6c05feb1d~:arch/arm/net/bpf_jit_32.c: >> bpf_jit_binary_lock_ro(header); >> 08f6c05feb1d~:arch/arm64/net/bpf_jit_comp.c: >> bpf_jit_binary_lock_ro(header); >> 08f6c05feb1d~:arch/loongarch/net/bpf_jit.c: >> bpf_jit_binary_lock_ro(header); >> 08f6c05feb1d~:arch/mips/net/bpf_jit_comp.c: >> bpf_jit_binary_lock_ro(header); >> 08f6c05feb1d~:arch/parisc/net/bpf_jit_core.c: >> bpf_jit_binary_lock_ro(jit_data->header); >> 08f6c05feb1d~:arch/s390/net/bpf_jit_comp.c: >> bpf_jit_binary_lock_ro(header); >> 08f6c05feb1d~:arch/sparc/net/bpf_jit_comp_64.c: >> bpf_jit_binary_lock_ro(header); >> 08f6c05feb1d~:arch/x86/net/bpf_jit_comp32.c: >> bpf_jit_binary_lock_ro(header); >> 08f6c05feb1d~:include/linux/filter.h:static inline void >> bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr) >> >> Therefore, commit 08f6c05feb1d should have included a backport for arm64. >> >> So yes, I agree with Greg, the correct fix should be to backport to >> ARM64 the changes done on other architectures in order to properly >> handle return of set_memory_rox() in bpf_jit_binary_lock_ro(). > > Ok, but it looks like due to this series, the powerpc tree is crashing > at the first bpf load, so something went wrong. Let me go revert these > 4 patches for now, and then I will be glad to queue them up if you can > provide a working series for all arches. > Fair enough, indeed I think for powerpc it probably also relies on more changes, so both ARM and POWERPC need a carefull backport. I can look at it, but can you tell why it was decided to apply that commit on stable at the first place ? Is there a particular need ? Thanks Christophe
