| Message ID | 20190108222044.4140262-1-songliubraving@fb.com |
|---|---|
| State | Accepted |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [bpf] bpf: fix panic in stack_map_get_build_id() on i386 and arm32 | expand |
> On Jan 8, 2019, at 2:20 PM, Song Liu <songliubraving@fb.com> wrote: > > As Naresh reported, test_stacktrace_build_id() causes panic on i386 and > arm32 systems. This is caused by page_address() returns NULL in certain > cases. > > This patch fixes this error by using kmap_atomic/kunmap_atomic instead > of page_address. > > Fixes: 615755a77b24 (" bpf: extend stackmap to save binary_build_id+offset instead of address") > Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> > Signed-off-by: Song Liu <songliubraving@fb.com> > --- > kernel/bpf/stackmap.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > index 90daf285de03..d9e2483669d0 100644 > --- a/kernel/bpf/stackmap.c > +++ b/kernel/bpf/stackmap.c > @@ -260,7 +260,7 @@ static int stack_map_get_build_id(struct vm_area_struct *vma, > return -EFAULT; /* page not mapped */ > > ret = -EINVAL; > - page_addr = page_address(page); > + page_addr = kmap_atomic(page); > ehdr = (Elf32_Ehdr *)page_addr; > > /* compare magic x7f "ELF" */ > @@ -276,6 +276,7 @@ static int stack_map_get_build_id(struct vm_area_struct *vma, > else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64) > ret = stack_map_get_build_id_64(page_addr, build_id); > out: > + kunmap_atomic(page_addr); > put_page(page); > return ret; > } > -- > 2.17.1 > Hi Naresh, I only tested this patch on i386 vm. Could you please help test it on ARM32 systems? Thanks, Song
On 01/08/2019 11:20 PM, Song Liu wrote: > As Naresh reported, test_stacktrace_build_id() causes panic on i386 and > arm32 systems. This is caused by page_address() returns NULL in certain > cases. > > This patch fixes this error by using kmap_atomic/kunmap_atomic instead > of page_address. > > Fixes: 615755a77b24 (" bpf: extend stackmap to save binary_build_id+offset instead of address") > Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> > Signed-off-by: Song Liu <songliubraving@fb.com> Looks correct to me, and in this case as per API the assumption is allowed that k[un]map_atomic() won't fail. I've applied it to bpf, if Naresh still replies with a Tested-by in time, I'll add it as well to the commit.
On Thu, 10 Jan 2019 at 20:56, Daniel Borkmann <daniel@iogearbox.net> wrote: > > On 01/08/2019 11:20 PM, Song Liu wrote: > > As Naresh reported, test_stacktrace_build_id() causes panic on i386 and > > arm32 systems. This is caused by page_address() returns NULL in certain > > cases. > > > > This patch fixes this error by using kmap_atomic/kunmap_atomic instead > > of page_address. > > > > Fixes: 615755a77b24 (" bpf: extend stackmap to save binary_build_id+offset instead of address") > > Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> > > Signed-off-by: Song Liu <songliubraving@fb.com> Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org> > > Looks correct to me, and in this case as per API the assumption is allowed > that k[un]map_atomic() won't fail. I've applied it to bpf, if Naresh still > replies with a Tested-by in time, I'll add it as well to the commit. This patch fixes the problem on Linux kernel 5.0.0-rc2. Thank you. Best regards Naresh Kamboju
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 90daf285de03..d9e2483669d0 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -260,7 +260,7 @@ static int stack_map_get_build_id(struct vm_area_struct *vma, return -EFAULT; /* page not mapped */ ret = -EINVAL; - page_addr = page_address(page); + page_addr = kmap_atomic(page); ehdr = (Elf32_Ehdr *)page_addr; /* compare magic x7f "ELF" */ @@ -276,6 +276,7 @@ static int stack_map_get_build_id(struct vm_area_struct *vma, else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64) ret = stack_map_get_build_id_64(page_addr, build_id); out: + kunmap_atomic(page_addr); put_page(page); return ret; }
As Naresh reported, test_stacktrace_build_id() causes panic on i386 and arm32 systems. This is caused by page_address() returns NULL in certain cases. This patch fixes this error by using kmap_atomic/kunmap_atomic instead of page_address. Fixes: 615755a77b24 (" bpf: extend stackmap to save binary_build_id+offset instead of address") Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by: Song Liu <songliubraving@fb.com> --- kernel/bpf/stackmap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)