Late arm64 fixes:

- Fix very early boot failures with KASLR enabled
 
 - Fix fatal signal handling on userspace access from kernel
 
 - Fix leakage of floating point register state across exec()
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Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fixes from Will Deacon:
 "Late arm64 fixes.

  They fix very early boot failures with KASLR where the early mapping
  of the kernel is incorrect, so the failure mode looks like a hang with
  no output. There's also a signal-handling fix when a uaccess routine
  faults with a fatal signal pending, which could be used to create
  unkillable user tasks using userfaultfd and finally a state leak fix
  for the floating pointer registers across a call to exec().

  We're still seeing some random issues crop up (inode memory corruption
  and spinlock recursion) but we've not managed to reproduce things
  reliably enough to debug or bisect them yet.

  Summary:

   - Fix very early boot failures with KASLR enabled

   - Fix fatal signal handling on userspace access from kernel

   - Fix leakage of floating point register state across exec()"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: kaslr: Adjust the offset to avoid Image across alignment boundary
  arm64: kaslr: ignore modulo offset when validating virtual displacement
  arm64: mm: abort uaccess retries upon fatal signal
  arm64: fpsimd: Prevent registers leaking across exec

arch/arm64/kernel/fpsimd.c

@@ -161,9 +161,11 @@ void fpsimd_flush_thread(void)
 {
 	if (!system_supports_fpsimd())
 		return;
+	preempt_disable();
 	memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
 	fpsimd_flush_task_state(current);
 	set_thread_flag(TIF_FOREIGN_FPSTATE);
+	preempt_enable();
 }
 
 /*

arch/arm64/kernel/head.S

@@ -354,7 +354,6 @@ __primary_switched:
 	tst	x23, ~(MIN_KIMG_ALIGN - 1)	// already running randomized?
 	b.ne	0f
 	mov	x0, x21				// pass FDT address in x0
-	mov	x1, x23				// pass modulo offset in x1
 	bl	kaslr_early_init		// parse FDT for KASLR options
 	cbz	x0, 0f				// KASLR disabled? just proceed
 	orr	x23, x23, x0			// record KASLR offset

arch/arm64/kernel/kaslr.c

@@ -75,7 +75,7 @@ extern void *__init __fixmap_remap_fdt(phys_addr_t dt_phys, int *size,
  * containing function pointers) to be reinitialized, and zero-initialized
  * .bss variables will be reset to 0.
  */
-u64 __init kaslr_early_init(u64 dt_phys, u64 modulo_offset)
+u64 __init kaslr_early_init(u64 dt_phys)
 {
 	void *fdt;
 	u64 seed, offset, mask, module_range;
@@ -131,15 +131,17 @@ u64 __init kaslr_early_init(u64 dt_phys, u64 modulo_offset)
 	/*
 	 * The kernel Image should not extend across a 1GB/32MB/512MB alignment
 	 * boundary (for 4KB/16KB/64KB granule kernels, respectively). If this
-	 * happens, increase the KASLR offset by the size of the kernel image
-	 * rounded up by SWAPPER_BLOCK_SIZE.
+	 * happens, round down the KASLR offset by (1 << SWAPPER_TABLE_SHIFT).
+	 *
+	 * NOTE: The references to _text and _end below will already take the
+	 *       modulo offset (the physical displacement modulo 2 MB) into
+	 *       account, given that the physical placement is controlled by
+	 *       the loader, and will not change as a result of the virtual
+	 *       mapping we choose.
 	 */
-	if ((((u64)_text + offset + modulo_offset) >> SWAPPER_TABLE_SHIFT) !=
-	    (((u64)_end + offset + modulo_offset) >> SWAPPER_TABLE_SHIFT)) {
-		u64 kimg_sz = _end - _text;
-		offset = (offset + round_up(kimg_sz, SWAPPER_BLOCK_SIZE))
-				& mask;
-	}
+	if ((((u64)_text + offset) >> SWAPPER_TABLE_SHIFT) !=
+	    (((u64)_end + offset) >> SWAPPER_TABLE_SHIFT))
+		offset = round_down(offset, 1 << SWAPPER_TABLE_SHIFT);
 
 	if (IS_ENABLED(CONFIG_KASAN))
 		/*

arch/arm64/mm/fault.c

@@ -435,8 +435,11 @@ retry:
 		 * the mmap_sem because it would already be released
 		 * in __lock_page_or_retry in mm/filemap.c.
 		 */
-		if (fatal_signal_pending(current))
+		if (fatal_signal_pending(current)) {
+			if (!user_mode(regs))
+				goto no_context;
 			return 0;
+		}
 
 		/*
 		 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk of