** Description changed:
Trusty 3.13 segfaults when running ldt_gdt_64 from the kernel's x86
selftests.
git bisect revealed that the following commit introduced the issue:
- 706276543b69 ("x86, extable: Switch to relative exception table entries")
+
+ commit aeb315d60afee129d32558f4a4b356eec2e7da7b
+ Author: Andy Lutomirski <l...@kernel.org>
+ Date: Thu Jul 30 14:31:32 2015 -0700
+
+ x86/ldt: Make modify_ldt synchronous
+
+ CVE-2017-5754
+
+ commit 37868fe113ff2ba814b3b4eb12df214df555f8dc upstream.
+
+ modify_ldt() has questionable locking and does not synchronize
+ threads. Improve it: redesign the locking and synchronize all
+ threads' LDTs using an IPI on all modifications.
+
+ This will dramatically slow down modify_ldt in multithreaded
+ programs, but there shouldn't be any multithreaded programs that
+ care about modify_ldt's performance in the first place.
+
+ This fixes some fallout from the CVE-2015-5157 fixes.
+
+ Signed-off-by: Andy Lutomirski <l...@kernel.org>
+ Reviewed-by: Borislav Petkov <b...@suse.de>
+ Cc: Andrew Cooper <andrew.coop...@citrix.com>
+ Cc: Andy Lutomirski <l...@amacapital.net>
+ Cc: Boris Ostrovsky <boris.ostrov...@oracle.com>
+ Cc: Borislav Petkov <b...@alien8.de>
+ Cc: Brian Gerst <brge...@gmail.com>
+ Cc: Denys Vlasenko <dvlas...@redhat.com>
+ Cc: H. Peter Anvin <h...@zytor.com>
+ Cc: Jan Beulich <jbeul...@suse.com>
+ Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
+ Cc: Linus Torvalds <torva...@linux-foundation.org>
+ Cc: Peter Zijlstra <pet...@infradead.org>
+ Cc: Sasha Levin <sasha.le...@oracle.com>
+ Cc: Steven Rostedt <rost...@goodmis.org>
+ Cc: Thomas Gleixner <t...@linutronix.de>
+ Link:
http://lkml.kernel.org/r/4c6978476782160600471bd865b318db34c7b628.1438291540.git.l...@kernel.org
+ Signed-off-by: Ingo Molnar <mi...@kernel.org>
+ Signed-off-by: Jiri Slaby <jsl...@suse.cz>
+ (cherry picked from commit 62fc7228f8cc8c89ecbd37008a0495ac28e41c5c)
+ Signed-off-by: Juerg Haefliger <juerg.haefli...@canonical.com>
+ Signed-off-by: Stefan Bader <stefan.ba...@canonical.com>
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https://bugs.launchpad.net/bugs/1755817
Title:
Segmentation fault in ldt_gdt_64
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