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| author |   Andy Lutomirski <luto@kernel.org> | 2018-08-29 08:47:18 -0700 |
|---|---|---|
| committer |   Thomas Gleixner <tglx@linutronix.de> | 2018-08-31 17:08:22 +0200 |
| commit | 4012e77a903d114f915fc607d6d2ed54a3d6c9b1 (patch) | |
| tree | aa56d63db999604dd3004855996dca36c293e1cf /arch/x86/mm/tlb.c | |
| parent | x86: Allow generating user-space headers without a compiler (diff) | |
| download | linux-dev-4012e77a903d114f915fc607d6d2ed54a3d6c9b1.tar.xz linux-dev-4012e77a903d114f915fc607d6d2ed54a3d6c9b1.zip | |
x86/nmi: Fix NMI uaccess race against CR3 switching
A NMI can hit in the middle of context switching or in the middle of
switch_mm_irqs_off(). In either case, CR3 might not match current->mm,
which could cause copy_from_user_nmi() and friends to read the wrong
memory.
Fix it by adding a new nmi_uaccess_okay() helper and checking it in
copy_from_user_nmi() and in __copy_from_user_nmi()'s callers.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jann Horn <jannh@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/dd956eba16646fd0b15c3c0741269dfd84452dac.1535557289.git.luto@kernel.org
Diffstat (limited to '')
| -rw-r--r-- | arch/x86/mm/tlb.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 9517d1b2a281..e96b99eb800c 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -305,6 +305,10 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, choose_new_asid(next, next_tlb_gen, &new_asid, &need_flush); + /* Let nmi_uaccess_okay() know that we're changing CR3. */ + this_cpu_write(cpu_tlbstate.loaded_mm, LOADED_MM_SWITCHING); + barrier(); + if (need_flush) { this_cpu_write(cpu_tlbstate.ctxs[new_asid].ctx_id, next->context.ctx_id); this_cpu_write(cpu_tlbstate.ctxs[new_asid].tlb_gen, next_tlb_gen); @@ -335,6 +339,9 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, if (next != &init_mm) this_cpu_write(cpu_tlbstate.last_ctx_id, next->context.ctx_id); + /* Make sure we write CR3 before loaded_mm. */ + barrier(); + this_cpu_write(cpu_tlbstate.loaded_mm, next); this_cpu_write(cpu_tlbstate.loaded_mm_asid, new_asid); } |