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author | Daniel Borkmann <daniel@iogearbox.net> | 2019-11-02 00:17:59 +0100 |
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committer | Alexei Starovoitov <ast@kernel.org> | 2019-11-02 12:39:12 -0700 |
commit | 6ae08ae3dea2cfa03dd3665a3c8475c2d429ef47 (patch) | |
tree | 7d89f1cc7074ea3cec0e35ab80490f653894dc72 /samples | |
parent | bpf: Make use of probe_user_write in probe write helper (diff) | |
download | wireguard-linux-6ae08ae3dea2cfa03dd3665a3c8475c2d429ef47.tar.xz wireguard-linux-6ae08ae3dea2cfa03dd3665a3c8475c2d429ef47.zip |
bpf: Add probe_read_{user, kernel} and probe_read_{user, kernel}_str helpers
The current bpf_probe_read() and bpf_probe_read_str() helpers are broken
in that they assume they can be used for probing memory access for kernel
space addresses /as well as/ user space addresses.
However, plain use of probe_kernel_read() for both cases will attempt to
always access kernel space address space given access is performed under
KERNEL_DS and some archs in-fact have overlapping address spaces where a
kernel pointer and user pointer would have the /same/ address value and
therefore accessing application memory via bpf_probe_read{,_str}() would
read garbage values.
Lets fix BPF side by making use of recently added 3d7081822f7f ("uaccess:
Add non-pagefault user-space read functions"). Unfortunately, the only way
to fix this status quo is to add dedicated bpf_probe_read_{user,kernel}()
and bpf_probe_read_{user,kernel}_str() helpers. The bpf_probe_read{,_str}()
helpers are kept as-is to retain their current behavior.
The two *_user() variants attempt the access always under USER_DS set, the
two *_kernel() variants will -EFAULT when accessing user memory if the
underlying architecture has non-overlapping address ranges, also avoiding
throwing the kernel warning via 00c42373d397 ("x86-64: add warning for
non-canonical user access address dereferences").
Fixes: a5e8c07059d0 ("bpf: add bpf_probe_read_str helper")
Fixes: 2541517c32be ("tracing, perf: Implement BPF programs attached to kprobes")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/796ee46e948bc808d54891a1108435f8652c6ca4.1572649915.git.daniel@iogearbox.net
Diffstat (limited to 'samples')
0 files changed, 0 insertions, 0 deletions