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authorPeter Zijlstra <peterz@infradead.org>2017-12-14 14:27:30 +0300
committerIngo Molnar <mingo@kernel.org>2017-12-22 22:13:01 +0300
commitc2b3496bb30bd159e9de42e5c952e1f1f33c9a77 (patch)
treed1617d48b0546def2ea19bc4a6fa3e1637e1f6ed /arch/x86/include/asm/mmu.h
parentc10e83f598d08046dd1ebc8360d4bb12d802d51b (diff)
downloadlinux-c2b3496bb30bd159e9de42e5c952e1f1f33c9a77.tar.xz
x86/ldt: Rework locking
The LDT is duplicated on fork() and on exec(), which is wrong as exec() should start from a clean state, i.e. without LDT. To fix this the LDT duplication code will be moved into arch_dup_mmap() which is only called for fork(). This introduces a locking problem. arch_dup_mmap() holds mmap_sem of the parent process, but the LDT duplication code needs to acquire mm->context.lock to access the LDT data safely, which is the reverse lock order of write_ldt() where mmap_sem nests into context.lock. Solve this by introducing a new rw semaphore which serializes the read/write_ldt() syscall operations and use context.lock to protect the actual installment of the LDT descriptor. So context.lock stabilizes mm->context.ldt and can nest inside of the new semaphore or mmap_sem. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@kernel.org> Cc: Andy Lutomirsky <luto@kernel.org> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bpetkov@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Laight <David.Laight@aculab.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Eduardo Valentin <eduval@amazon.com> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will.deacon@arm.com> Cc: aliguori@amazon.com Cc: dan.j.williams@intel.com Cc: hughd@google.com Cc: keescook@google.com Cc: kirill.shutemov@linux.intel.com Cc: linux-mm@kvack.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/mmu.h')
-rw-r--r--arch/x86/include/asm/mmu.h4
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index 9ea26f167497..5ff3e8af2c20 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -3,6 +3,7 @@
#define _ASM_X86_MMU_H
#include <linux/spinlock.h>
+#include <linux/rwsem.h>
#include <linux/mutex.h>
#include <linux/atomic.h>
@@ -27,7 +28,8 @@ typedef struct {
atomic64_t tlb_gen;
#ifdef CONFIG_MODIFY_LDT_SYSCALL
- struct ldt_struct *ldt;
+ struct rw_semaphore ldt_usr_sem;
+ struct ldt_struct *ldt;
#endif
#ifdef CONFIG_X86_64