Hi! On Sun 2019-05-26 12:25:27, Hugh Dickins wrote: > On Sun, 26 May 2019, Sebastian Andrzej Siewior wrote: > > On 2019-05-26 19:33:25 [+0200], To Hugh Dickins wrote: > > From: Hugh Dickins <hughd@xxxxxxxxxx> > > … > > > Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> > > > > Hugh, I took your patch, slapped a signed-off-by line. Please say that > > you are fine with it (or object otherwise). > > I'm fine with it, thanks Sebastian. Sorry if I wasted your time by not > giving it my sign-off in the first place, but I was not comfortable to > dabble there without your sign-off too - which it now has. (And thought > you might already have your own version anyway: just provided mine as > illustration, so that we could be sure of exactly what I'd been testing.) I applied Hugh's patch on top of -rc2, but still get emacs problems: But this time I'm not sure if it is same emacs problem or different emacs problem.... X protocol error: BadValue (integer parameter out of range for operation) on protocol request 139 When compiled with GTK, Emacs cannot recover from X disconnects. This is a GTK bug: https://bugzilla.gnome.org/show_bug.cgi?id=85715 For details, see etc/PROBLEMS. (emacs:8175): GLib-WARNING **: g_main_context_prepare() called recursively from within a source's check() or prepare() member. (emacs:8175): GLib-WARNING **: g_main_context_check() called recursively from within a source's check() or prepare() member. Fatal error 6: Aborted Backtrace: emacs[0x8138719] emacs[0x8120446] emacs[0x813875c] emacs[0x80f54c0] emacs[0x80f6f3f] emacs[0x80f6fab] /usr/lib/i386-linux-gnu/libX11.so.6(_XError+0x11a)[0xf6ea1b3a] /usr/lib/i386-linux-gnu/libX11.so.6(+0x39b5b)[0xf6e9eb5b] /usr/lib/i386-linux-gnu/libX11.so.6(+0x39c26)[0xf6e9ec26] /usr/lib/i386-linux-gnu/libX11.so.6(_XEventsQueued+0x6e)[0xf6e9f4be] /usr/lib/i386-linux-gnu/libX11.so.6(XPending+0x62)[0xf6e90752] /usr/lib/i386-linux-gnu/libgdk-3.so.0(+0x48073)[0xf7566073] /lib/i386-linux-gnu/libglib-2.0.so.0(g_main_context_prepare+0x17b)[0xf70244fb] /lib/i386-linux-gnu/libglib-2.0.so.0(+0x46f74)[0xf7024f74] /lib/i386-linux-gnu/libglib-2.0.so.0(g_main_context_pending+0x34)[0xf7025144] /usr/lib/i386-linux-gnu/libgtk-3.so.0(gtk_events_pending+0x1f)[0xf77c9a8f] emacs[0x80f55a9] emacs[0x812714f] emacs[0x8126a95] emacs[0x8172db9] emacs[0x8192bd7] emacs[0x819312d] emacs[0x8125634] emacs[0x8125c6d] emacs[0x812725b] emacs[0x8129eaa] emacs[0x81c7c90] emacs[0x8127815] emacs[0x812ada3] emacs[0x812bdad] emacs[0x812d838] emacs[0x818b76c] emacs[0x8120890] emacs[0x818b66b] emacs[0x8124b84] emacs[0x8124e3f] emacs[0x8059cb0] /lib/i386-linux-gnu/i686/cmov/libc.so.6(__libc_start_main+0xf3)[0xf61a7a63] emacs[0x805a76f] Aborted (core dumped) Best regards, Pavel commit 018c9da72adf920efd0ba250fcf433b836d3cfbc Author: Hugh Dickins <hughd@xxxxxxxxxx> Date: Sun May 26 19:33:25 2019 +0200 x86/fpu: Use fault_in_pages_writeable() for pre-faulting Since commit d9c9ce34ed5c8 ("x86/fpu: Fault-in user stack if copy_fpstate_to_sigframe() fails") we use get_user_pages_unlocked() to pre-faulting user's memory if a write generates a page fault while the handler is disabled. This works in general and uncovered a bug as reported by Mike Rapoport. It has been pointed out that this function may be fragile and a simple pre-fault as in fault_in_pages_writeable() would be a better solution. Better as in taste and simplicity: That write (as performed by the alternative function) performs exactly the same faulting of memory that we had before. This was suggested by Hugh Dickins and Andrew Morton. Use fault_in_pages_writeable() for pre-faulting of user's stack. Suggested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> Link: https://lkml.kernel.org/r/alpine.LSU.2.11.1905251033230.1112@eggly.anvils [bigeasy: patch description] Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c index 5a8d118..060d618 100644 --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -5,6 +5,7 @@ #include <linux/compat.h> #include <linux/cpu.h> +#include <linux/pagemap.h> #include <asm/fpu/internal.h> #include <asm/fpu/signal.h> @@ -189,15 +190,7 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) fpregs_unlock(); if (ret) { - int aligned_size; - int nr_pages; - - aligned_size = offset_in_page(buf_fx) + fpu_user_xstate_size; - nr_pages = DIV_ROUND_UP(aligned_size, PAGE_SIZE); - - ret = get_user_pages_unlocked((unsigned long)buf_fx, nr_pages, - NULL, FOLL_WRITE); - if (ret == nr_pages) + if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size)) goto retry; return -EFAULT; } -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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