On Tue, Oct 01, 2013 at 06:33:04AM +0100, AKASHI Takahiro wrote:
In ftrace_syscall_enter(), syscall_get_arguments(..., 0, n, ...) if (i == 0) { <handle orig_x0> ...; n--;} memcpy(..., n * sizeof(args[0])); If 'number of arguments(n)' is zero and 'argument index(i)' is also zero in syscall_get_arguments(), none of arguments should be copied by memcpy(). Otherwise 'n--' can be a big positive number and unexpected amount of data will be copied. Tracing system calls which take no argument, say sync(void), may hit this case and eventually make the system corrupted. This patch fixes the issue both in syscall_get_arguments() and syscall_set_arguments().
Please note, however, that asm-generic/syscall.h says,
- syscall_get_arguments - extract system call parameter values
- @i: argument index [0,5]
- @n: number of arguments; n+i must be [1,6].
and so we'd better change the caller's code(ftrace_syscall_enter).
Since (most) other architectures deal with n+i == 0, please can you submit a separate patch updating that comment?
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org
arch/arm64/include/asm/syscall.h | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h index c89821f..01bb8cc 100644 --- a/arch/arm64/include/asm/syscall.h +++ b/arch/arm64/include/asm/syscall.h @@ -63,6 +63,9 @@ static inline void syscall_get_arguments(struct task_struct *task, unsigned int i, unsigned int n, unsigned long *args) {
- if (n == 0)
return;- if (i + n > SYSCALL_MAX_ARGS) { unsigned long *args_bad = args + SYSCALL_MAX_ARGS - i; unsigned int n_bad = n + i - SYSCALL_MAX_ARGS;
@@ -86,6 +89,9 @@ static inline void syscall_set_arguments(struct task_struct *task, unsigned int i, unsigned int n, const unsigned long *args) {
- if (n == 0)
return;
Looks sensible. Please can you fix arch/arm/ as well?
Cheers,
Will