ptrace_get_syscall_info() is potentially copying uninitialized stack memory to userspace, since the compiler may leave a 3-byte hole near the beginning of `info`. Fix it by adding a padding field to `struct ptrace_syscall_info`.
Cc: [email protected] Fixes: 201766a20e30 ("ptrace: add PTRACE_GET_SYSCALL_INFO request") Suggested-by: Dan Carpenter <[email protected]> Signed-off-by: Peilin Ye <[email protected]> --- Change in v3: - Remove unnecessary `__aligned__` attribute. (Suggested by Dmitry V. Levin <[email protected]>) Change in v2: - Add a padding field to `struct ptrace_syscall_info`, instead of doing memset() on `info`. (Suggested by Dmitry V. Levin <[email protected]>) Reference: https://lwn.net/Articles/417989/ $ # before: $ pahole -C "ptrace_syscall_info" kernel/ptrace.o struct ptrace_syscall_info { __u8 op; /* 0 1 */ /* XXX 3 bytes hole, try to pack */ __u32 arch __attribute__((__aligned__(4))); /* 4 4 */ __u64 instruction_pointer; /* 8 8 */ __u64 stack_pointer; /* 16 8 */ union { struct { __u64 nr; /* 24 8 */ __u64 args[6]; /* 32 48 */ } entry; /* 24 56 */ struct { __s64 rval; /* 24 8 */ __u8 is_error; /* 32 1 */ } exit; /* 24 16 */ struct { __u64 nr; /* 24 8 */ __u64 args[6]; /* 32 48 */ /* --- cacheline 1 boundary (64 bytes) was 16 bytes ago --- */ __u32 ret_data; /* 80 4 */ } seccomp; /* 24 64 */ }; /* 24 64 */ /* size: 88, cachelines: 2, members: 5 */ /* sum members: 85, holes: 1, sum holes: 3 */ /* forced alignments: 1, forced holes: 1, sum forced holes: 3 */ /* last cacheline: 24 bytes */ } __attribute__((__aligned__(8))); $ $ # after: $ pahole -C "ptrace_syscall_info" kernel/ptrace.o struct ptrace_syscall_info { __u8 op; /* 0 1 */ __u8 pad[3]; /* 1 3 */ __u32 arch; /* 4 4 */ __u64 instruction_pointer; /* 8 8 */ __u64 stack_pointer; /* 16 8 */ union { struct { __u64 nr; /* 24 8 */ __u64 args[6]; /* 32 48 */ } entry; /* 24 56 */ struct { __s64 rval; /* 24 8 */ __u8 is_error; /* 32 1 */ } exit; /* 24 16 */ struct { __u64 nr; /* 24 8 */ __u64 args[6]; /* 32 48 */ /* --- cacheline 1 boundary (64 bytes) was 16 bytes ago --- */ __u32 ret_data; /* 80 4 */ } seccomp; /* 24 64 */ }; /* 24 64 */ /* size: 88, cachelines: 2, members: 6 */ /* last cacheline: 24 bytes */ }; $ _ include/uapi/linux/ptrace.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h index a71b6e3b03eb..83ee45fa634b 100644 --- a/include/uapi/linux/ptrace.h +++ b/include/uapi/linux/ptrace.h @@ -81,7 +81,8 @@ struct seccomp_metadata { struct ptrace_syscall_info { __u8 op; /* PTRACE_SYSCALL_INFO_* */ - __u32 arch __attribute__((__aligned__(sizeof(__u32)))); + __u8 pad[3]; + __u32 arch; __u64 instruction_pointer; __u64 stack_pointer; union { -- 2.25.1
