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authorEric Dumazet <edumazet@google.com>2019-11-01 04:34:44 +0100
committerDaniel Borkmann <daniel@iogearbox.net>2019-11-02 00:32:26 +0100
commit7de086909365cd60a5619a45af3f4152516fd75c (patch)
tree877ccc41536b3d95a334706daf59dcce52ef7d9d /arch
parentbpf: Change size to u64 for bpf_map_{area_alloc, charge_init}() (diff)
downloadlinux-7de086909365cd60a5619a45af3f4152516fd75c.tar.xz
linux-7de086909365cd60a5619a45af3f4152516fd75c.zip
powerpc/bpf: Fix tail call implementation
We have seen many crashes on powerpc hosts while loading bpf programs. The problem here is that bpf_int_jit_compile() does a first pass to compute the program length. Then it allocates memory to store the generated program and calls bpf_jit_build_body() a second time (and a third time later) What I have observed is that the second bpf_jit_build_body() could end up using few more words than expected. If bpf_jit_binary_alloc() put the space for the program at the end of the allocated page, we then write on a non mapped memory. It appears that bpf_jit_emit_tail_call() calls bpf_jit_emit_common_epilogue() while ctx->seen might not be stable. Only after the second pass we can be sure ctx->seen wont be changed. Trying to avoid a second pass seems quite complex and probably not worth it. Fixes: ce0761419faef ("powerpc/bpf: Implement support for tail calls") Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com> Cc: Sandipan Das <sandipan@linux.ibm.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Martin KaFai Lau <kafai@fb.com> Cc: Song Liu <songliubraving@fb.com> Cc: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/20191101033444.143741-1-edumazet@google.com
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/net/bpf_jit_comp64.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index 02a59946a78a..be3517ef0574 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -1142,6 +1142,19 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
}
/*
+ * If we have seen a tail call, we need a second pass.
+ * This is because bpf_jit_emit_common_epilogue() is called
+ * from bpf_jit_emit_tail_call() with a not yet stable ctx->seen.
+ */
+ if (cgctx.seen & SEEN_TAILCALL) {
+ cgctx.idx = 0;
+ if (bpf_jit_build_body(fp, 0, &cgctx, addrs, false)) {
+ fp = org_fp;
+ goto out_addrs;
+ }
+ }
+
+ /*
* Pretend to build prologue, given the features we've seen. This will
* update ctgtx.idx as it pretends to output instructions, then we can
* calculate total size from idx.