Luke Nelson 4178417cc5 arm, bpf: Fix offset overflow for BPF_MEM BPF_DW ... This patch fixes an incorrect check in how immediate memory offsets are computed for BPF_DW on arm. For BPF_LDX/ST/STX + BPF_DW, the 32-bit arm JIT breaks down an 8-byte access into two separate 4-byte accesses using off+0 and off+4. If off fits in imm12, the JIT emits a ldr/str instruction with the immediate and avoids the use of a temporary register. While the current check off <= 0xfff ensures that the first immediate off+0 doesn't overflow imm12, it's not sufficient for the second immediate off+4, which may cause the second access of BPF_DW to read/write the wrong address. This patch fixes the problem by changing the check to off <= 0xfff - 4 for BPF_DW, ensuring off+4 will never overflow. A side effect of simplifying the check is that it now allows using negative immediate offsets in ldr/str. This means that small negative offsets can also avoid the use of a temporary register. This patch introduces no new failures in test_verifier or test_bpf.c. Fixes: c5eae69257 ("ARM: net: bpf: improve 64-bit store implementation") Fixes: ec19e02b34 ("ARM: net: bpf: fix LDX instructions") Co-developed-by: Xi Wang <xi.wang@gmail.com> Signed-off-by: Xi Wang <xi.wang@gmail.com> Signed-off-by: Luke Nelson <luke.r.nels@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20200409221752.28448-1-luke.r.nels@gmail.com		2020-04-14 21:27:54 +02:00
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bpf_jit_32.c	arm, bpf: Fix offset overflow for BPF_MEM BPF_DW	2020-04-14 21:27:54 +02:00
bpf_jit_32.h	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441	2019-06-05 17:37:17 +02:00
Makefile	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00