On Wed, 17 Oct 2018 16:59:51 -0400 Steven Rostedt <rost...@goodmis.org> wrote:
> From: "Steven Rostedt (VMware)" <rost...@goodmis.org> > > Andy had some concerns about using regs_get_kernel_stack_nth() in a new > function regs_get_kernel_argument() as if there's any error in the stack > code, it could cause a bad memory access. To be on the safe side, call > probe_kernel_read() on the stack address to be extra careful in accessing > the memory. A helper function, regs_get_kernel_stack_nth_addr(), was added > to just return the stack address (or NULL if not on the stack), that will be > used to find the address (and could be used by other functions) and read the > address with kernel_probe_read(). > > Link: > http://lkml.kernel.org/r/calcetrxn9zktb9i1lp3qofcpqzhf34bdkuz5d3n0ucmrr+v...@mail.gmail.com > Requested-by: Andy Lutomirski <l...@amacapital.net> > Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org> Looks good to me. Reviewed-by: Masami Hiramatsu <mhira...@kernel.org> Thank you, > --- > > Changes since v1: > > - Make regs_get_kernel_stack_nth() not fault, and not have a > separate function. Only tracing uses it anyway. > > arch/x86/include/asm/ptrace.h | 43 > ++++++++++++++++++++++++++++++++++++------- > 1 file changed, 36 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h > index c2304b25e2fd..055f632ce711 100644 > --- a/arch/x86/include/asm/ptrace.h > +++ b/arch/x86/include/asm/ptrace.h > @@ -237,23 +237,52 @@ static inline int regs_within_kernel_stack(struct > pt_regs *regs, > } > > /** > + * regs_get_kernel_stack_nth_addr() - get the address of the Nth entry on > stack > + * @regs: pt_regs which contains kernel stack pointer. > + * @n: stack entry number. > + * > + * regs_get_kernel_stack_nth() returns the address of the @n th entry of the > + * kernel stack which is specified by @regs. If the @n th entry is NOT in > + * the kernel stack, this returns NULL. > + */ > +static inline unsigned long *regs_get_kernel_stack_nth_addr(struct pt_regs > *regs, > + unsigned int n) > +{ > + unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs); > + > + addr += n; > + if (regs_within_kernel_stack(regs, (unsigned long)addr)) > + return addr; > + else > + return NULL; > +} > + > +/* To avoid include hell, we can't include uaccess.h */ > +extern long probe_kernel_read(void *dst, const void *src, size_t size); > + > +/** > * regs_get_kernel_stack_nth() - get Nth entry of the stack > * @regs: pt_regs which contains kernel stack pointer. > * @n: stack entry number. > * > * regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which > - * is specified by @regs. If the @n th entry is NOT in the kernel stack, > + * is specified by @regs. If the @n th entry is NOT in the kernel stack > * this returns 0. > */ > static inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs, > unsigned int n) > { > - unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs); > - addr += n; > - if (regs_within_kernel_stack(regs, (unsigned long)addr)) > - return *addr; > - else > - return 0; > + unsigned long *addr; > + unsigned long val; > + long ret; > + > + addr = regs_get_kernel_stack_nth_addr(regs, n); > + if (addr) { > + ret = probe_kernel_read(&val, addr, sizeof(val)); > + if (!ret) > + return val; > + } > + return 0; > } > > /** > -- > 2.13.6 > -- Masami Hiramatsu <mhira...@kernel.org>
