Trying to boot tip/master resulted in: |DMAR: dmar0: Using Queued invalidation |DMAR: dmar1: Using Queued invalidation |DMAR: Setting RMRR: |DMAR: Setting identity map for device 0000:00:1a.0 [0xbdcf9000 - 0xbdd1dfff] |BUG: unable to handle kernel NULL pointer dereference at (null) |IP: __domain_mapping+0x10f/0x3d0 |PGD 0 |P4D 0 | |Oops: 0002 [#1] PREEMPT SMP |Modules linked in: |CPU: 19 PID: 1 Comm: swapper/0 Not tainted 4.12.0-rc6-00117-g235a93822a21 #113 |task: ffff8805271c2c80 task.stack: ffffc90000058000 |RIP: 0010:__domain_mapping+0x10f/0x3d0 |RSP: 0000:ffffc9000005bca0 EFLAGS: 00010246 |RAX: 0000000000000000 RBX: 00000000bdcf9003 RCX: 0000000000000000 |RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001 |RBP: ffffc9000005bd00 R08: ffff880a243e9780 R09: ffff8805259e67c8 |R10: 00000000000bdcf9 R11: 0000000000000000 R12: 0000000000000025 |R13: 0000000000000025 R14: 0000000000000000 R15: 00000000000bdcf9 |FS: 0000000000000000(0000) GS:ffff88052acc0000(0000) knlGS:0000000000000000 |CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 |CR2: 0000000000000000 CR3: 0000000001c0f000 CR4: 00000000000406e0 |Call Trace: | iommu_domain_identity_map+0x5a/0x80 | domain_prepare_identity_map+0x9f/0x160 | iommu_prepare_identity_map+0x7e/0x9b bisect points to commit 235a93822a21 ("locking/atomics, asm-generic: Add KASAN instrumentation to atomic operations"), RIP is at tmp = cmpxchg64_local(&pte->val, 0ULL, pteval); in drivers/iommu/intel-iommu.c. The assembly for this inline assembly is: xor %edx,%edx xor %eax,%eax cmpxchg %rbx,(%rdx) and as you see edx is set to zero and used later as a pointer via the full register. This happens with gcc-6, 5 and 8 (snapshot from last week). After a longer while of searching and swearing I figured out that this bug occures once cmpxchg64_local() and cmpxchg_local() uses the same ____ptr macro and they are shadow somehow. What I don't know why edx is set to zero. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> --- include/asm-generic/atomic-instrumented.h | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/include/asm-generic/atomic-instrumented.h b/include/asm-generic/atomic-instrumented.h index a0f5b7525bb2..ac6155362b39 100644 --- a/include/asm-generic/atomic-instrumented.h +++ b/include/asm-generic/atomic-instrumented.h @@ -359,16 +359,16 @@ static __always_inline bool atomic64_add_negative(s64 i, atomic64_t *v) #define cmpxchg64(ptr, old, new) \ ({ \ - __typeof__(ptr) ____ptr = (ptr); \ - kasan_check_write(____ptr, sizeof(*____ptr)); \ - arch_cmpxchg64(____ptr, (old), (new)); \ + __typeof__(ptr) ____ptr64 = (ptr); \ + kasan_check_write(____ptr64, sizeof(*____ptr64));\ + arch_cmpxchg64(____ptr64, (old), (new)); \ }) #define cmpxchg64_local(ptr, old, new) \ ({ \ - __typeof__(ptr) ____ptr = (ptr); \ - kasan_check_write(____ptr, sizeof(*____ptr)); \ - arch_cmpxchg64_local(____ptr, (old), (new)); \ + __typeof__(ptr) ____ptr64 = (ptr); \ + kasan_check_write(____ptr64, sizeof(*____ptr64));\ + arch_cmpxchg64_local(____ptr64, (old), (new)); \ }) #define cmpxchg_double(p1, p2, o1, o2, n1, n2) \ -- 2.13.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>