> There is a set of syscalls in the kernel about 'sigaction'. > All they end up with calling the helper 'do_sigaction', > so the generic scheme is: > > - copy user data to kernel; > - 'do_sigaction'; > - copy kernel data to user. > > 'do_sigaction' checks 'signum' parameter before doing its main job. > If this check fails syscall fails immediately, as well. But at this > stage first copy is already done. And so there's a potential chance > having it useless. It may affect performance significantly if user > data was, say, swapped, and a fault was handled to obtain it. Only if the signal number is wrong? So why do we care? > In this patch, 'signum' sanity check is moved out of 'do_sigaction' > to a small function 'user_signal'. So we can call it before any copying. ... > arch/alpha/kernel/signal.c | 19 +++++++------- > arch/mips/kernel/signal.c | 10 +++++--- > arch/mips/kernel/signal32.c | 10 +++++--- > arch/sparc/kernel/sys_sparc32.c | 10 ++++---- > arch/sparc/kernel/sys_sparc_32.c | 10 ++++---- > arch/sparc/kernel/sys_sparc_64.c | 10 ++++---- > include/linux/sched.h | 2 +- > include/linux/signal.h | 5 ++++ > kernel/signal.c | 54 +++++++++++++++++++++------------------- > 9 files changed, 71 insertions(+), 59 deletions(-) And this blows the source and compiled code. Not too much, but this change should be justified somehow. And to me this patch doesn't look like a cleanup, imho this sanity check makes more sense in one place. Oleg.
