| Message ID | 20230918155233.297024-3-memxor@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 00b7e8f4c02d75fa3a34a39a591afd951cfce837 |
| Delegated to: | BPF |
| Headers | show |
| Series | Fixes for Exceptions | expand |
Hi Kumar, On 18/09/2023 17:52, Kumar Kartikeya Dwivedi wrote: > On 32-bit architectures, the pointer width is 32-bit, while we try to > cast from a u64 down to it, the compiler complains on mismatch in > integer size. Fix this by first casting to long which should match > the pointer width on targets supported by Linux. Thank you for the patch, it fixes the issue on our side! (Not sure you need a tested by tag but just in case: ) Tested-by: Matthieu Baerts <matthieu.baerts@tessares.net> > Fixes: ec5290a178b7 ("bpf: Prevent KASAN false positive with bpf_throw") > Reported-by: Matthieu Baerts <matthieu.baerts@tessares.net> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> > --- > kernel/bpf/helpers.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index 7ff2a42f1996..dd1c69ee3375 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -2488,7 +2488,7 @@ __bpf_kfunc void bpf_throw(u64 cookie) > * deeper stack depths than ctx.sp as we do not return from bpf_throw, > * which skips compiler generated instrumentation to do the same. > */ > - kasan_unpoison_task_stack_below((void *)ctx.sp); > + kasan_unpoison_task_stack_below((void *)(long)ctx.sp); I never know what's the recommended way to fix such issues: casting it to 'long' or 'unsigned long'? But it looks like both are used in the kernel and 'long' is more often used than the other one so all good I suppose. > ctx.aux->bpf_exception_cb(cookie, ctx.sp, ctx.bp); > WARN(1, "A call to BPF exception callback should never return\n"); > } Cheers, Matt
On 9/18/23 10:09, Matthieu Baerts wrote: > Hi Kumar, > > On 18/09/2023 17:52, Kumar Kartikeya Dwivedi wrote: >> On 32-bit architectures, the pointer width is 32-bit, while we try to >> cast from a u64 down to it, the compiler complains on mismatch in >> integer size. Fix this by first casting to long which should match >> the pointer width on targets supported by Linux. > > Thank you for the patch, it fixes the issue on our side! > > (Not sure you need a tested by tag but just in case: ) > > Tested-by: Matthieu Baerts <matthieu.baerts@tessares.net> > >> Fixes: ec5290a178b7 ("bpf: Prevent KASAN false positive with bpf_throw") >> Reported-by: Matthieu Baerts <matthieu.baerts@tessares.net> >> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> >> --- >> kernel/bpf/helpers.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c >> index 7ff2a42f1996..dd1c69ee3375 100644 >> --- a/kernel/bpf/helpers.c >> +++ b/kernel/bpf/helpers.c >> @@ -2488,7 +2488,7 @@ __bpf_kfunc void bpf_throw(u64 cookie) >> * deeper stack depths than ctx.sp as we do not return from bpf_throw, >> * which skips compiler generated instrumentation to do the same. >> */ >> - kasan_unpoison_task_stack_below((void *)ctx.sp); >> + kasan_unpoison_task_stack_below((void *)(long)ctx.sp); > I never know what's the recommended way to fix such issues: casting it > to 'long' or 'unsigned long'? But it looks like both are used in the > kernel and 'long' is more often used than the other one so all good I > suppose. Shouldn't we have a macro to do this kind of casting if there is not? Without any comment, it is difficult to know why this extra casting is here. > >> ctx.aux->bpf_exception_cb(cookie, ctx.sp, ctx.bp); >> WARN(1, "A call to BPF exception callback should never return\n"); >> } > > Cheers, > Matt
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 7ff2a42f1996..dd1c69ee3375 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2488,7 +2488,7 @@ __bpf_kfunc void bpf_throw(u64 cookie) * deeper stack depths than ctx.sp as we do not return from bpf_throw, * which skips compiler generated instrumentation to do the same. */ - kasan_unpoison_task_stack_below((void *)ctx.sp); + kasan_unpoison_task_stack_below((void *)(long)ctx.sp); ctx.aux->bpf_exception_cb(cookie, ctx.sp, ctx.bp); WARN(1, "A call to BPF exception callback should never return\n"); }
On 32-bit architectures, the pointer width is 32-bit, while we try to cast from a u64 down to it, the compiler complains on mismatch in integer size. Fix this by first casting to long which should match the pointer width on targets supported by Linux. Fixes: ec5290a178b7 ("bpf: Prevent KASAN false positive with bpf_throw") Reported-by: Matthieu Baerts <matthieu.baerts@tessares.net> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> --- kernel/bpf/helpers.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)