From d895a0f16fadb26d22ab531c49768f7642ae5c3e Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Fri, 16 Aug 2019 12:53:00 +0200 Subject: bpf: fix accessing bpf_sysctl.file_pos on s390 "ctx:file_pos sysctl:read write ok" fails on s390 with "Read value != nux". This is because verifier rewrites a complete 32-bit bpf_sysctl.file_pos update to a partial update of the first 32 bits of 64-bit *bpf_sysctl_kern.ppos, which is not correct on big-endian systems. Fix by using an offset on big-endian systems. Ditto for bpf_sysctl.file_pos reads. Currently the test does not detect a problem there, since it expects to see 0, which it gets with high probability in error cases, so change it to seek to offset 3 and expect 3 in bpf_sysctl.file_pos. Fixes: e1550bfe0de4 ("bpf: Add file_pos field to bpf_sysctl ctx") Signed-off-by: Ilya Leoshkevich Acked-by: Yonghong Song Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20190816105300.49035-1-iii@linux.ibm.com/ --- include/linux/filter.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'include/linux') diff --git a/include/linux/filter.h b/include/linux/filter.h index 92c6e31fb008..2ce57645f3cd 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -749,14 +749,14 @@ bpf_ctx_narrow_access_ok(u32 off, u32 size, u32 size_default) } static inline u8 -bpf_ctx_narrow_load_shift(u32 off, u32 size, u32 size_default) +bpf_ctx_narrow_access_offset(u32 off, u32 size, u32 size_default) { - u8 load_off = off & (size_default - 1); + u8 access_off = off & (size_default - 1); #ifdef __LITTLE_ENDIAN - return load_off * 8; + return access_off; #else - return (size_default - (load_off + size)) * 8; + return size_default - (access_off + size); #endif } -- cgit