Merge tag 'for-linus-5.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml

Pull UML updates from Richard Weinberger:

 - KASAN support for x86_64

 - noreboot command line option, just like qemu's -no-reboot

 - Various fixes and cleanups

* tag 'for-linus-5.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml:
  um: include sys/types.h for size_t
  um: Replace to_phys() and to_virt() with less generic function names
  um: Add missing apply_returns()
  um: add "noreboot" command line option for PANIC_TIMEOUT=-1 setups
  um: include linux/stddef.h for __always_inline
  UML: add support for KASAN under x86_64
  mm: Add PAGE_ALIGN_DOWN macro
  um: random: Don't initialise hwrng struct with zero
  um: remove unused mm_copy_segments
  um: remove unused variable
  um: Remove straying parenthesis
  um: x86: print RIP with symbol
  arch: um: Fix build for statically linked UML w/ constructors
  x86/um: Kconfig: Fix indentation
  um/drivers: Kconfig: Fix indentation
  um: Kconfig: Fix indentation

23 files changed, 196 insertions, 53 deletions

diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 4ec22e156a2e3..78de31ac1da7c 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -12,6 +12,8 @@ config UML
 	select ARCH_HAS_STRNLEN_USER
 	select ARCH_NO_PREEMPT
 	select HAVE_ARCH_AUDITSYSCALL
+	select HAVE_ARCH_KASAN if X86_64
+	select HAVE_ARCH_KASAN_VMALLOC if HAVE_ARCH_KASAN
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_UID16
@@ -82,7 +84,7 @@ config ARCH_HAS_CACHE_LINE_SIZE
 source "arch/$(HEADER_ARCH)/um/Kconfig"
 
 config MAY_HAVE_RUNTIME_DEPS
-        bool
+	bool
 
 config STATIC_LINK
 	bool "Force a static link"
@@ -219,6 +221,19 @@ config UML_TIME_TRAVEL_SUPPORT
 
 	  It is safe to say Y, but you probably don't need this.
 
+config KASAN_SHADOW_OFFSET
+	hex
+	depends on KASAN
+	default 0x100000000000
+	help
+	  This is the offset at which the ~16TB of shadow memory is
+	  mapped and used by KASAN for memory debugging. This can be any
+	  address that has at least KASAN_SHADOW_SIZE (total address space divided
+	  by 8) amount of space so that the KASAN shadow memory does not conflict
+	  with anything. The default is 0x100000000000, which works even if mem is
+	  set to a large value. On low-memory systems, try 0x7fff8000, as it fits
+	  into the immediate of most instructions, improving performance.
+
 endmenu
 
 source "arch/um/drivers/Kconfig"
diff --git a/arch/um/drivers/Kconfig b/arch/um/drivers/Kconfig
index 914da774bd390..5903e2b598aae 100644
--- a/arch/um/drivers/Kconfig
+++ b/arch/um/drivers/Kconfig
@@ -251,37 +251,37 @@ config UML_NET_VECTOR
 	depends on UML_NET
 	select MAY_HAVE_RUNTIME_DEPS
 	help
-	This User-Mode Linux network driver uses multi-message send
-	and receive functions. The host running the UML guest must have
-	a linux kernel version above 3.0 and a libc version > 2.13.
-	This driver provides tap, raw, gre and l2tpv3 network transports
-	with up to 4 times higher network throughput than the UML network
-	drivers.
+	  This User-Mode Linux network driver uses multi-message send
+	  and receive functions. The host running the UML guest must have
+	  a linux kernel version above 3.0 and a libc version > 2.13.
+	  This driver provides tap, raw, gre and l2tpv3 network transports
+	  with up to 4 times higher network throughput than the UML network
+	  drivers.
 
 config UML_NET_VDE
 	bool "VDE transport (obsolete)"
 	depends on UML_NET
 	select MAY_HAVE_RUNTIME_DEPS
 	help
-	This User-Mode Linux network transport allows one or more running
-	UMLs on a single host to communicate with each other and also
-	with the rest of the world using Virtual Distributed Ethernet,
-	an improved fork of uml_switch.
+	  This User-Mode Linux network transport allows one or more running
+	  UMLs on a single host to communicate with each other and also
+	  with the rest of the world using Virtual Distributed Ethernet,
+	  an improved fork of uml_switch.
 
-	You must have libvdeplug installed in order to build the vde
-	transport into UML.
+	  You must have libvdeplug installed in order to build the vde
+	  transport into UML.
 
-	To use this form of networking, you will need to run vde_switch
-	on the host.
+	  To use this form of networking, you will need to run vde_switch
+	  on the host.
 
-	For more information, see <http://wiki.virtualsquare.org/>
-	That site has a good overview of what VDE is and also examples
-	of the UML command line to use to enable VDE networking.
+	  For more information, see <http://wiki.virtualsquare.org/>
+	  That site has a good overview of what VDE is and also examples
+	  of the UML command line to use to enable VDE networking.
 
-	NOTE: THIS TRANSPORT IS DEPRECATED AND WILL BE REMOVED SOON!!! Please
-	migrate to UML_NET_VECTOR.
+	  NOTE: THIS TRANSPORT IS DEPRECATED AND WILL BE REMOVED SOON!!! Please
+	  migrate to UML_NET_VECTOR.
 
-	If unsure, say N.
+	  If unsure, say N.
 
 config UML_NET_MCAST
 	bool "Multicast transport (obsolete)"
@@ -311,19 +311,19 @@ config UML_NET_PCAP
 	depends on UML_NET
 	select MAY_HAVE_RUNTIME_DEPS
 	help
-	The pcap transport makes a pcap packet stream on the host look
-	like an ethernet device inside UML.  This is useful for making
-	UML act as a network monitor for the host.  You must have libcap
-	installed in order to build the pcap transport into UML.
+	  The pcap transport makes a pcap packet stream on the host look
+	  like an ethernet device inside UML.  This is useful for making
+	  UML act as a network monitor for the host.  You must have libcap
+	  installed in order to build the pcap transport into UML.
 
 	  For more information, see
 	  <http://user-mode-linux.sourceforge.net/old/networking.html>  That site
 	  has examples of the UML command line to use to enable this option.
 
-	NOTE: THIS TRANSPORT IS DEPRECATED AND WILL BE REMOVED SOON!!! Please
-	migrate to UML_NET_VECTOR.
+	  NOTE: THIS TRANSPORT IS DEPRECATED AND WILL BE REMOVED SOON!!! Please
+	  migrate to UML_NET_VECTOR.
 
-	If unsure, say N.
+	  If unsure, say N.
 
 config UML_NET_SLIRP
 	bool "SLiRP transport (obsolete)"
diff --git a/arch/um/drivers/random.c b/arch/um/drivers/random.c
index 433a3f8f2ef3e..32b3341fe9707 100644
--- a/arch/um/drivers/random.c
+++ b/arch/um/drivers/random.c
@@ -28,7 +28,7 @@
  * protects against a module being loaded twice at the same time.
  */
 static int random_fd = -1;
-static struct hwrng hwrng = { 0, };
+static struct hwrng hwrng;
 static DECLARE_COMPLETION(have_data);
 
 static int rng_dev_read(struct hwrng *rng, void *buf, size_t max, bool block)
diff --git a/arch/um/include/asm/common.lds.S b/arch/um/include/asm/common.lds.S
index eca6c452a41bd..fd481ac371de0 100644
--- a/arch/um/include/asm/common.lds.S
+++ b/arch/um/include/asm/common.lds.S
@@ -83,6 +83,8 @@
   }
   .init_array : {
 	__init_array_start = .;
+	*(.kasan_init)
+	*(.init_array.*)
 	*(.init_array)
 	__init_array_end = .;
   }
diff --git a/arch/um/include/asm/kasan.h b/arch/um/include/asm/kasan.h
new file mode 100644
index 0000000000000..0d6547f4ec85c
--- /dev/null
+++ b/arch/um/include/asm/kasan.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_UM_KASAN_H
+#define __ASM_UM_KASAN_H
+
+#include <linux/init.h>
+#include <linux/const.h>
+
+#define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
+
+/* used in kasan_mem_to_shadow to divide by 8 */
+#define KASAN_SHADOW_SCALE_SHIFT 3
+
+#ifdef CONFIG_X86_64
+#define KASAN_HOST_USER_SPACE_END_ADDR 0x00007fffffffffffUL
+/* KASAN_SHADOW_SIZE is the size of total address space divided by 8 */
+#define KASAN_SHADOW_SIZE ((KASAN_HOST_USER_SPACE_END_ADDR + 1) >> \
+			KASAN_SHADOW_SCALE_SHIFT)
+#else
+#error "KASAN_SHADOW_SIZE is not defined for this sub-architecture"
+#endif /* CONFIG_X86_64 */
+
+#define KASAN_SHADOW_START (KASAN_SHADOW_OFFSET)
+#define KASAN_SHADOW_END (KASAN_SHADOW_START + KASAN_SHADOW_SIZE)
+
+#ifdef CONFIG_KASAN
+void kasan_init(void);
+void kasan_map_memory(void *start, unsigned long len);
+extern int kasan_um_is_ready;
+
+#ifdef CONFIG_STATIC_LINK
+#define kasan_arch_is_ready() (kasan_um_is_ready)
+#endif
+#else
+static inline void kasan_init(void) { }
+#endif /* CONFIG_KASAN */
+
+#endif /* __ASM_UM_KASAN_H */
diff --git a/arch/um/include/asm/processor-generic.h b/arch/um/include/asm/processor-generic.h
index 6a4fe8b4e686b..d0fc1862da957 100644
--- a/arch/um/include/asm/processor-generic.h
+++ b/arch/um/include/asm/processor-generic.h
@@ -59,11 +59,6 @@ static inline void release_thread(struct task_struct *task)
 {
 }
 
-static inline void mm_copy_segments(struct mm_struct *from_mm,
-				    struct mm_struct *new_mm)
-{
-}
-
 /*
  * User space process size: 3GB (default).
  */
diff --git a/arch/um/include/asm/xor.h b/arch/um/include/asm/xor.h
index 22b39de73c246..647fae200c5d3 100644
--- a/arch/um/include/asm/xor.h
+++ b/arch/um/include/asm/xor.h
@@ -18,7 +18,7 @@
 #undef XOR_SELECT_TEMPLATE
 /* pick an arbitrary one - measuring isn't possible with inf-cpu */
 #define XOR_SELECT_TEMPLATE(x)	\
-	(time_travel_mode == TT_MODE_INFCPU ? TT_CPU_INF_XOR_DEFAULT : x))
+	(time_travel_mode == TT_MODE_INFCPU ? TT_CPU_INF_XOR_DEFAULT : x)
 #endif
 
 #endif
diff --git a/arch/um/include/shared/user.h b/arch/um/include/shared/user.h
index dd4badffdeb3d..bda66e5a9d4e3 100644
--- a/arch/um/include/shared/user.h
+++ b/arch/um/include/shared/user.h
@@ -16,11 +16,12 @@
  */
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
 
-/* This is to get size_t */
+/* This is to get size_t and NULL */
 #ifndef __UM_HOST__
 #include <linux/types.h>
 #else
 #include <stddef.h>
+#include <sys/types.h>
 #endif
 
 extern void panic(const char *fmt, ...)
diff --git a/arch/um/kernel/dyn.lds.S b/arch/um/kernel/dyn.lds.S
index 2f2a8ce92f1ee..2b7fc5b541648 100644
--- a/arch/um/kernel/dyn.lds.S
+++ b/arch/um/kernel/dyn.lds.S
@@ -109,7 +109,11 @@ SECTIONS
      be empty, which isn't pretty.  */
   . = ALIGN(32 / 8);
   .preinit_array     : { *(.preinit_array) }
-  .init_array     : { *(.init_array) }
+  .init_array     : {
+    *(.kasan_init)
+    *(.init_array.*)
+    *(.init_array)
+  }
   .fini_array     : { *(.fini_array) }
   .data           : {
     INIT_TASK_DATA(KERNEL_STACK_SIZE)
diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index 15295c3237a00..276a1f0b91f1a 100644
--- a/arch/um/kernel/mem.c
+++ b/arch/um/kernel/mem.c
@@ -18,6 +18,25 @@
 #include <kern_util.h>
 #include <mem_user.h>
 #include <os.h>
+#include <linux/sched/task.h>
+
+#ifdef CONFIG_KASAN
+int kasan_um_is_ready;
+void kasan_init(void)
+{
+	/*
+	 * kasan_map_memory will map all of the required address space and
+	 * the host machine will allocate physical memory as necessary.
+	 */
+	kasan_map_memory((void *)KASAN_SHADOW_START, KASAN_SHADOW_SIZE);
+	init_task.kasan_depth = 0;
+	kasan_um_is_ready = true;
+}
+
+static void (*kasan_init_ptr)(void)
+__section(".kasan_init") __used
+= kasan_init;
+#endif
 
 /* allocated in paging_init, zeroed in mem_init, and unchanged thereafter */
 unsigned long *empty_zero_page = NULL;
diff --git a/arch/um/kernel/stacktrace.c b/arch/um/kernel/stacktrace.c
index 86df52168bd94..fd3b61b3d4d2b 100644
--- a/arch/um/kernel/stacktrace.c
+++ b/arch/um/kernel/stacktrace.c
@@ -27,7 +27,7 @@ void dump_trace(struct task_struct *tsk,
 
 	frame = (struct stack_frame *)bp;
 	while (((long) sp & (THREAD_SIZE-1)) != 0) {
-		addr = *sp;
+		addr = READ_ONCE_NOCHECK(*sp);
 		if (__kernel_text_address(addr)) {
 			reliable = 0;
 			if ((unsigned long) sp == bp + sizeof(long)) {
diff --git a/arch/um/kernel/uml.lds.S b/arch/um/kernel/uml.lds.S
index 7a8e2b123e29c..71a59b8adbdca 100644
--- a/arch/um/kernel/uml.lds.S
+++ b/arch/um/kernel/uml.lds.S
@@ -95,6 +95,7 @@ SECTIONS
   }
 
   .got           : { *(.got.plt) *(.got) }
+  .eh_frame       : { KEEP (*(.eh_frame)) }
   .dynamic       : { *(.dynamic) }
   .tdata	  : { *(.tdata .tdata.* .gnu.linkonce.td.*) }
   .tbss		  : { *(.tbss .tbss.* .gnu.linkonce.tb.*) *(.tcommon) }
diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c
index 3c1b77474d2d1..8530b2e086049 100644
--- a/arch/um/os-Linux/mem.c
+++ b/arch/um/os-Linux/mem.c
@@ -17,6 +17,28 @@
 #include <init.h>
 #include <os.h>
 
+/*
+ * kasan_map_memory - maps memory from @start with a size of @len.
+ * The allocated memory is filled with zeroes upon success.
+ * @start: the start address of the memory to be mapped
+ * @len: the length of the memory to be mapped
+ *
+ * This function is used to map shadow memory for KASAN in uml
+ */
+void kasan_map_memory(void *start, size_t len)
+{
+	if (mmap(start,
+		 len,
+		 PROT_READ|PROT_WRITE,
+		 MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE,
+		 -1,
+		 0) == MAP_FAILED) {
+		os_info("Couldn't allocate shadow memory: %s\n.",
+			strerror(errno));
+		exit(1);
+	}
+}
+
 /* Set by make_tempfile() during early boot. */
 static char *tempdir = NULL;
 
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index c316c993a9491..b24db6017ded6 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -5,6 +5,7 @@
  */
 
 #include <stdlib.h>
+#include <stdbool.h>
 #include <unistd.h>
 #include <sched.h>
 #include <errno.h>
@@ -707,10 +708,24 @@ void halt_skas(void)
 	UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
 }
 
+static bool noreboot;
+
+static int __init noreboot_cmd_param(char *str, int *add)
+{
+	noreboot = true;
+	return 0;
+}
+
+__uml_setup("noreboot", noreboot_cmd_param,
+"noreboot\n"
+"    Rather than rebooting, exit always, akin to QEMU's -no-reboot option.\n"
+"    This is useful if you're using CONFIG_PANIC_TIMEOUT in order to catch\n"
+"    crashes in CI\n");
+
 void reboot_skas(void)
 {
 	block_signals_trace();
-	UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT);
+	UML_LONGJMP(&initial_jmpbuf, noreboot ? INIT_JMP_HALT : INIT_JMP_REBOOT);
 }
 
 void __switch_mm(struct mm_id *mm_idp)
diff --git a/arch/um/os-Linux/umid.c b/arch/um/os-Linux/umid.c
index a3dd61521d240..7a1abb8299307 100644
--- a/arch/um/os-Linux/umid.c
+++ b/arch/um/os-Linux/umid.c
@@ -136,7 +136,7 @@ out:
 static inline int is_umdir_used(char *dir)
 {
 	char pid[sizeof("nnnnnnnnn")], *end, *file;
-	int dead, fd, p, n, err;
+	int fd, p, n, err;
 	size_t filelen = strlen(dir) + sizeof("/pid") + 1;
 
 	file = malloc(filelen);
@@ -145,7 +145,6 @@ static inline int is_umdir_used(char *dir)
 
 	snprintf(file, filelen, "%s/pid", dir);
 
-	dead = 0;
 	fd = open(file, O_RDONLY);
 	if (fd < 0) {
 		fd = -errno;
diff --git a/arch/um/os-Linux/user_syms.c b/arch/um/os-Linux/user_syms.c
index 715594fe57190..cb667c9225abd 100644
--- a/arch/um/os-Linux/user_syms.c
+++ b/arch/um/os-Linux/user_syms.c
@@ -27,10 +27,10 @@ EXPORT_SYMBOL(strstr);
 #ifndef __x86_64__
 extern void *memcpy(void *, const void *, size_t);
 EXPORT_SYMBOL(memcpy);
-#endif
-
 EXPORT_SYMBOL(memmove);
 EXPORT_SYMBOL(memset);
+#endif
+
 EXPORT_SYMBOL(printf);
 
 /* Here, instead, I can provide a fake prototype. Yes, someone cares: genksyms.
diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig
index 1bcd42c530394..186f13268401b 100644
--- a/arch/x86/um/Kconfig
+++ b/arch/x86/um/Kconfig
@@ -32,12 +32,12 @@ config 3_LEVEL_PGTABLES
 	bool "Three-level pagetables" if !64BIT
 	default 64BIT
 	help
-	Three-level pagetables will let UML have more than 4G of physical
-	memory.  All the memory that can't be mapped directly will be treated
-	as high memory.
+	  Three-level pagetables will let UML have more than 4G of physical
+	  memory.  All the memory that can't be mapped directly will be treated
+	  as high memory.
 
-	However, this it experimental on 32-bit architectures, so if unsure say
-	N (on x86-64 it's automatically enabled, instead, as it's safe there).
+	  However, this it experimental on 32-bit architectures, so if unsure say
+	  N (on x86-64 it's automatically enabled, instead, as it's safe there).
 
 config ARCH_HAS_SC_SIGNALS
 	def_bool !64BIT
diff --git a/arch/x86/um/Makefile b/arch/x86/um/Makefile
index ba5789c358094..f778e37494bab 100644
--- a/arch/x86/um/Makefile
+++ b/arch/x86/um/Makefile
@@ -28,7 +28,8 @@ else
 
 obj-y += syscalls_64.o vdso/
 
-subarch-y = ../lib/csum-partial_64.o ../lib/memcpy_64.o ../entry/thunk_64.o
+subarch-y = ../lib/csum-partial_64.o ../lib/memcpy_64.o ../entry/thunk_64.o \
+	../lib/memmove_64.o ../lib/memset_64.o
 
 endif
 
diff --git a/arch/x86/um/shared/sysdep/stub_64.h b/arch/x86/um/shared/sysdep/stub_64.h
index e9c4b2b388039..92ea1670cf1c8 100644
--- a/arch/x86/um/shared/sysdep/stub_64.h
+++ b/arch/x86/um/shared/sysdep/stub_64.h
@@ -8,6 +8,7 @@
 
 #include <sysdep/ptrace_user.h>
 #include <generated/asm-offsets.h>
+#include <linux/stddef.h>
 
 #define STUB_MMAP_NR __NR_mmap
 #define MMAP_OFFSET(o) (o)
diff --git a/arch/x86/um/sysrq_64.c b/arch/x86/um/sysrq_64.c
index 903ad91b624f2..ef1eb4f4f6126 100644
--- a/arch/x86/um/sysrq_64.c
+++ b/arch/x86/um/sysrq_64.c
@@ -19,8 +19,8 @@ void show_regs(struct pt_regs *regs)
 	print_modules();
 	printk(KERN_INFO "Pid: %d, comm: %.20s %s %s\n", task_pid_nr(current),
 		current->comm, print_tainted(), init_utsname()->release);
-	printk(KERN_INFO "RIP: %04lx:[<%016lx>]\n", PT_REGS_CS(regs) & 0xffff,
-	       PT_REGS_IP(regs));
+	printk(KERN_INFO "RIP: %04lx:%pS\n", PT_REGS_CS(regs) & 0xffff,
+	       (void *)PT_REGS_IP(regs));
 	printk(KERN_INFO "RSP: %016lx  EFLAGS: %08lx\n", PT_REGS_SP(regs),
 	       PT_REGS_EFLAGS(regs));
 	printk(KERN_INFO "RAX: %016lx RBX: %016lx RCX: %016lx\n",
diff --git a/arch/x86/um/vdso/Makefile b/arch/x86/um/vdso/Makefile
index 5943387e3f357..8c0396fd0e6f6 100644
--- a/arch/x86/um/vdso/Makefile
+++ b/arch/x86/um/vdso/Makefile
@@ -3,6 +3,9 @@
 # Building vDSO images for x86.
 #
 
+# do not instrument on vdso because KASAN is not compatible with user mode
+KASAN_SANITIZE			:= n
+
 # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
 KCOV_INSTRUMENT                := n
 
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7898e29bcfb54..a37b8c062daa6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -221,6 +221,9 @@ int overcommit_policy_handler(struct ctl_table *, int, void *, size_t *,
 /* to align the pointer to the (next) page boundary */
 #define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE)
 
+/* to align the pointer to the (prev) page boundary */
+#define PAGE_ALIGN_DOWN(addr) ALIGN_DOWN(addr, PAGE_SIZE)
+
 /* test whether an address (unsigned long or pointer) is aligned to PAGE_SIZE */
 #define PAGE_ALIGNED(addr)	IS_ALIGNED((unsigned long)(addr), PAGE_SIZE)
 
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index a4f07de217711..0e3648b603a6f 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -295,9 +295,22 @@ int kasan_populate_vmalloc(unsigned long addr, unsigned long size)
 		return 0;
 
 	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr);
-	shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
 	shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size);
-	shadow_end = ALIGN(shadow_end, PAGE_SIZE);
+
+	/*
+	 * User Mode Linux maps enough shadow memory for all of virtual memory
+	 * at boot, so doesn't need to allocate more on vmalloc, just clear it.
+	 *
+	 * The remaining CONFIG_UML checks in this file exist for the same
+	 * reason.
+	 */
+	if (IS_ENABLED(CONFIG_UML)) {
+		__memset((void *)shadow_start, KASAN_VMALLOC_INVALID, shadow_end - shadow_start);
+		return 0;
+	}
+
+	shadow_start = PAGE_ALIGN_DOWN(shadow_start);
+	shadow_end = PAGE_ALIGN(shadow_end);
 
 	ret = apply_to_page_range(&init_mm, shadow_start,
 				  shadow_end - shadow_start,
@@ -466,6 +479,10 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
 
 	if (shadow_end > shadow_start) {
 		size = shadow_end - shadow_start;
+		if (IS_ENABLED(CONFIG_UML)) {
+			__memset(shadow_start, KASAN_SHADOW_INIT, shadow_end - shadow_start);
+			return;
+		}
 		apply_to_existing_page_range(&init_mm,
 					     (unsigned long)shadow_start,
 					     size, kasan_depopulate_vmalloc_pte,
@@ -531,6 +548,11 @@ int kasan_alloc_module_shadow(void *addr, size_t size, gfp_t gfp_mask)
 	if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
 		return -EINVAL;
 
+	if (IS_ENABLED(CONFIG_UML)) {
+		__memset((void *)shadow_start, KASAN_SHADOW_INIT, shadow_size);
+		return 0;
+	}
+
 	ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 			shadow_start + shadow_size,
 			GFP_KERNEL,
@@ -554,6 +576,9 @@ int kasan_alloc_module_shadow(void *addr, size_t size, gfp_t gfp_mask)
 
 void kasan_free_module_shadow(const struct vm_struct *vm)
 {
+	if (IS_ENABLED(CONFIG_UML))
+		return;
+
 	if (vm->flags & VM_KASAN)
 		vfree(kasan_mem_to_shadow(vm->addr));
 }