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c2b3496bb3
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>
66 lines
1.6 KiB
C
66 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_MMU_H
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#define _ASM_X86_MMU_H
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#include <linux/spinlock.h>
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#include <linux/rwsem.h>
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#include <linux/mutex.h>
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#include <linux/atomic.h>
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/*
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* x86 has arch-specific MMU state beyond what lives in mm_struct.
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*/
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typedef struct {
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/*
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* ctx_id uniquely identifies this mm_struct. A ctx_id will never
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* be reused, and zero is not a valid ctx_id.
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*/
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u64 ctx_id;
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/*
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* Any code that needs to do any sort of TLB flushing for this
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* mm will first make its changes to the page tables, then
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* increment tlb_gen, then flush. This lets the low-level
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* flushing code keep track of what needs flushing.
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*
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* This is not used on Xen PV.
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*/
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atomic64_t tlb_gen;
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#ifdef CONFIG_MODIFY_LDT_SYSCALL
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struct rw_semaphore ldt_usr_sem;
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struct ldt_struct *ldt;
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#endif
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#ifdef CONFIG_X86_64
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/* True if mm supports a task running in 32 bit compatibility mode. */
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unsigned short ia32_compat;
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#endif
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struct mutex lock;
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void __user *vdso; /* vdso base address */
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const struct vdso_image *vdso_image; /* vdso image in use */
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atomic_t perf_rdpmc_allowed; /* nonzero if rdpmc is allowed */
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#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
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/*
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* One bit per protection key says whether userspace can
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* use it or not. protected by mmap_sem.
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*/
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u16 pkey_allocation_map;
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s16 execute_only_pkey;
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#endif
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#ifdef CONFIG_X86_INTEL_MPX
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/* address of the bounds directory */
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void __user *bd_addr;
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#endif
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} mm_context_t;
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#define INIT_MM_CONTEXT(mm) \
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.context = { \
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.ctx_id = 1, \
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}
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void leave_mm(int cpu);
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#endif /* _ASM_X86_MMU_H */
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