Merge tag 'printk-for-5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek: - Stop synchronizing kernel log buffer readers by logbuf_lock. As a result, the access to the buffer is fully lockless now. Note that printk() itself still uses locks because it tries to flush the messages to the console immediately. Also the per-CPU temporary buffers are still there because they prevent infinite recursion and serialize backtraces from NMI. All this is going to change in the future. - kmsg_dump API rework and cleanup as a side effect of the logbuf_lock removal. - Make bstr_printf() aware that %pf and %pF formats could deference the given pointer. - Show also page flags by %pGp format. - Clarify the documentation for plain pointer printing. - Do not show no_hash_pointers warning multiple times. - Update Senozhatsky email address. - Some clean up. * tag 'printk-for-5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: (24 commits) lib/vsprintf.c: remove leftover 'f' and 'F' cases from bstr_printf() printk: clarify the documentation for plain pointer printing kernel/printk.c: Fixed mundane typos printk: rename vprintk_func to vprintk vsprintf: dump full information of page flags in pGp mm, slub: don't combine pr_err with INFO mm, slub: use pGp to print page flags MAINTAINERS: update Senozhatsky email address lib/vsprintf: do not show no_hash_pointers message multiple times printk: console: remove unnecessary safe buffer usage printk: kmsg_dump: remove _nolock() variants printk: remove logbuf_lock printk: introduce a kmsg_dump iterator printk: kmsg_dumper: remove @active field printk: add syslog_lock printk: use atomic64_t for devkmsg_user.seq printk: use seqcount_latch for clear_seq printk: introduce CONSOLE_LOG_MAX printk: consolidate kmsg_dump_get_buffer/syslog_print_all code printk: refactor kmsg_dump_get_buffer() ...
2026-03-06 15:25:10 -08:00 · 2021-04-27 18:09:44 -07:00
parent 916a75965e c8dbea6df3
commit 7f3d08b255
16 changed files with 502 additions and 340 deletions
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -79,7 +79,19 @@ Pointers printed without a specifier extension (i.e unadorned %p) are
 hashed to prevent leaking information about the kernel memory layout. This
 has the added benefit of providing a unique identifier. On 64-bit machines
 the first 32 bits are zeroed. The kernel will print ``(ptrval)`` until it
-gathers enough entropy. If you *really* want the address see %px below.
+gathers enough entropy.
+
+When possible, use specialised modifiers such as %pS or %pB (described below)
+to avoid the need of providing an unhashed address that has to be interpreted
+post-hoc. If not possible, and the aim of printing the address is to provide
+more information for debugging, use %p and boot the kernel with the
+``no_hash_pointers`` parameter during debugging, which will print all %p
+addresses unmodified. If you *really* always want the unmodified address, see
+%px below.
+
+If (and only if) you are printing addresses as a content of a virtual file in
+e.g. procfs or sysfs (using e.g. seq_printf(), not printk()) read by a
+userspace process, use the %pK modifier described below instead of %p or %px.

 Error Pointers
 --------------
@@ -139,6 +151,11 @@ For printing kernel pointers which should be hidden from unprivileged
 users. The behaviour of %pK depends on the kptr_restrict sysctl - see
 Documentation/admin-guide/sysctl/kernel.rst for more details.

+This modifier is *only* intended when producing content of a file read by
+userspace from e.g. procfs or sysfs, not for dmesg. Please refer to the
+section about %p above for discussion about how to manage hashing pointers
+in printk().
+
 Unmodified Addresses
 --------------------

@@ -153,6 +170,13 @@ equivalent to %lx (or %lu). %px is preferred because it is more uniquely
 grep'able. If in the future we need to modify the way the kernel handles
 printing pointers we will be better equipped to find the call sites.

+Before using %px, consider if using %p is sufficient together with enabling the
+``no_hash_pointers`` kernel parameter during debugging sessions (see the %p
+description above). One valid scenario for %px might be printing information
+immediately before a panic, which prevents any sensitive information to be
+exploited anyway, and with %px there would be no need to reproduce the panic
+with no_hash_pointers.
+
 Pointer Differences
 -------------------

@@ -540,7 +564,7 @@ Flags bitfields such as page flags, gfp_flags

 ::

-	%pGp	referenced|uptodate|lru|active|private
+	%pGp	referenced|uptodate|lru|active|private|node=0|zone=2|lastcpupid=0x1fffff
 	%pGg	GFP_USER|GFP_DMA32|GFP_NOWARN
 	%pGv	read|exec|mayread|maywrite|mayexec|denywrite

--- a/8
+++ b/8
@@ -14535,7 +14535,7 @@ F:	kernel/sched/psi.c

 PRINTK
 M:	Petr Mladek <pmladek@suse.com>
-M:	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+M:	Sergey Senozhatsky <senozhatsky@chromium.org>
 R:	Steven Rostedt <rostedt@goodmis.org>
 R:	John Ogness <john.ogness@linutronix.de>
 S:	Maintained
@@ -19388,7 +19388,7 @@ F:	drivers/net/vrf.c
 VSPRINTF
 M:	Petr Mladek <pmladek@suse.com>
 M:	Steven Rostedt <rostedt@goodmis.org>
-M:	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+M:	Sergey Senozhatsky <senozhatsky@chromium.org>
 R:	Andy Shevchenko <andriy.shevchenko@linux.intel.com>
 R:	Rasmus Villemoes <linux@rasmusvillemoes.dk>
 S:	Maintained
@@ -20039,7 +20039,7 @@ F:	drivers/staging/media/zoran/
 ZRAM COMPRESSED RAM BLOCK DEVICE DRVIER
 M:	Minchan Kim <minchan@kernel.org>
 M:	Nitin Gupta <ngupta@vflare.org>
-R:	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
+R:	Sergey Senozhatsky <senozhatsky@chromium.org>
 L:	linux-kernel@vger.kernel.org
 S:	Maintained
 F:	Documentation/admin-guide/blockdev/zram.rst
@@ -20053,7 +20053,7 @@ F:	drivers/tty/serial/zs.*
 ZSMALLOC COMPRESSED SLAB MEMORY ALLOCATOR
 M:	Minchan Kim <minchan@kernel.org>
 M:	Nitin Gupta <ngupta@vflare.org>
-R:	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
+R:	Sergey Senozhatsky <senozhatsky@chromium.org>
 L:	linux-mm@kvack.org
 S:	Maintained
 F:	Documentation/vm/zsmalloc.rst
--- a/arch/powerpc/kernel/nvram_64.c
+++ b/arch/powerpc/kernel/nvram_64.c
@@ -647,6 +647,7 @@ static void oops_to_nvram(struct kmsg_dumper *dumper,
 {
 	struct oops_log_info *oops_hdr = (struct oops_log_info *)oops_buf;
 	static unsigned int oops_count = 0;
+	static struct kmsg_dump_iter iter;
 	static bool panicking = false;
 	static DEFINE_SPINLOCK(lock);
 	unsigned long flags;
@@ -681,13 +682,14 @@ static void oops_to_nvram(struct kmsg_dumper *dumper,
 		return;

 	if (big_oops_buf) {
-		kmsg_dump_get_buffer(dumper, false,
+		kmsg_dump_rewind(&iter);
+		kmsg_dump_get_buffer(&iter, false,
 				     big_oops_buf, big_oops_buf_sz, &text_len);
 		rc = zip_oops(text_len);
 	}
 	if (rc != 0) {
-		kmsg_dump_rewind(dumper);
-		kmsg_dump_get_buffer(dumper, false,
+		kmsg_dump_rewind(&iter);
+		kmsg_dump_get_buffer(&iter, false,
 				     oops_data, oops_data_sz, &text_len);
 		err_type = ERR_TYPE_KERNEL_PANIC;
 		oops_hdr->version = cpu_to_be16(OOPS_HDR_VERSION);
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -3001,7 +3001,7 @@ print_address(unsigned long addr)
 static void
 dump_log_buf(void)
 {
-	struct kmsg_dumper dumper = { .active = 1 };
+	struct kmsg_dump_iter iter;
 	unsigned char buf[128];
 	size_t len;

@@ -3013,9 +3013,9 @@ dump_log_buf(void)
 	catch_memory_errors = 1;
 	sync();

-	kmsg_dump_rewind_nolock(&dumper);
+	kmsg_dump_rewind(&iter);
 	xmon_start_pagination();
-	while (kmsg_dump_get_line_nolock(&dumper, false, buf, sizeof(buf), &len)) {
+	while (kmsg_dump_get_line(&iter, false, buf, sizeof(buf), &len)) {
 		buf[len] = '\0';
 		printf("%s", buf);
 	}
--- a/arch/um/kernel/kmsg_dump.c
+++ b/arch/um/kernel/kmsg_dump.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/kmsg_dump.h>
+#include <linux/spinlock.h>
 #include <linux/console.h>
 #include <linux/string.h>
 #include <shared/init.h>
@@ -9,8 +10,11 @@
 static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
 				enum kmsg_dump_reason reason)
 {
+	static struct kmsg_dump_iter iter;
+	static DEFINE_SPINLOCK(lock);
 	static char line[1024];
 	struct console *con;
+	unsigned long flags;
 	size_t len = 0;

 	/* only dump kmsg when no console is available */
@@ -29,11 +33,18 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
 	if (con)
 		return;

+	if (!spin_trylock_irqsave(&lock, flags))
+		return;
+
+	kmsg_dump_rewind(&iter);
+
 	printf("kmsg_dump:\n");
-	while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) {
+	while (kmsg_dump_get_line(&iter, true, line, sizeof(line), &len)) {
 		line[len] = '\0';
 		printf("%s", line);
 	}
+
+	spin_unlock_irqrestore(&lock, flags);
 }

 static struct kmsg_dumper kmsg_dumper = {
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1399,6 +1399,7 @@ static irqreturn_t vmbus_percpu_isr(int irq, void *dev_id)
 static void hv_kmsg_dump(struct kmsg_dumper *dumper,
 			 enum kmsg_dump_reason reason)
 {
+	struct kmsg_dump_iter iter;
 	size_t bytes_written;

 	/* We are only interested in panics. */
@@ -1409,7 +1410,8 @@ static void hv_kmsg_dump(struct kmsg_dumper *dumper,
 	 * Write dump contents to the page. No need to synchronize; panic should
 	 * be single-threaded.
 	 */
-	kmsg_dump_get_buffer(dumper, false, hv_panic_page, HV_HYP_PAGE_SIZE,
+	kmsg_dump_rewind(&iter);
+	kmsg_dump_get_buffer(&iter, false, hv_panic_page, HV_HYP_PAGE_SIZE,
 			     &bytes_written);
 	if (!bytes_written)
 		return;
--- a/drivers/mtd/mtdoops.c
+++ b/drivers/mtd/mtdoops.c
@@ -52,6 +52,7 @@ static struct mtdoops_context {
 	int nextcount;
 	unsigned long *oops_page_used;

+	unsigned long oops_buf_busy;
 	void *oops_buf;
 } oops_cxt;

@@ -180,6 +181,9 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic)
 	u32 *hdr;
 	int ret;

+	if (test_and_set_bit(0, &cxt->oops_buf_busy))
+		return;
+
 	/* Add mtdoops header to the buffer */
 	hdr = cxt->oops_buf;
 	hdr[0] = cxt->nextcount;
@@ -190,7 +194,7 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic)
 				      record_size, &retlen, cxt->oops_buf);
 		if (ret == -EOPNOTSUPP) {
 			printk(KERN_ERR "mtdoops: Cannot write from panic without panic_write\n");
-			return;
+			goto out;
 		}
 	} else
 		ret = mtd_write(mtd, cxt->nextpage * record_size,
@@ -203,6 +207,8 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic)
 	memset(cxt->oops_buf, 0xff, record_size);

 	mtdoops_inc_counter(cxt);
+out:
+	clear_bit(0, &cxt->oops_buf_busy);
 }

 static void mtdoops_workfunc_write(struct work_struct *work)
@@ -271,13 +277,19 @@ static void mtdoops_do_dump(struct kmsg_dumper *dumper,
 {
 	struct mtdoops_context *cxt = container_of(dumper,
 			struct mtdoops_context, dump);
+	struct kmsg_dump_iter iter;

 	/* Only dump oopses if dump_oops is set */
 	if (reason == KMSG_DUMP_OOPS && !dump_oops)
 		return;

-	kmsg_dump_get_buffer(dumper, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE,
+	kmsg_dump_rewind(&iter);
+
+	if (test_and_set_bit(0, &cxt->oops_buf_busy))
+		return;
+	kmsg_dump_get_buffer(&iter, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE,
 			     record_size - MTDOOPS_HEADER_SIZE, NULL);
+	clear_bit(0, &cxt->oops_buf_busy);

 	if (reason != KMSG_DUMP_OOPS) {
 		/* Panics must be written immediately */
@@ -394,6 +406,7 @@ static int __init mtdoops_init(void)
 		return -ENOMEM;
 	}
 	memset(cxt->oops_buf, 0xff, record_size);
+	cxt->oops_buf_busy = 0;

 	INIT_WORK(&cxt->work_erase, mtdoops_workfunc_erase);
 	INIT_WORK(&cxt->work_write, mtdoops_workfunc_write);
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -385,6 +385,7 @@ void pstore_record_init(struct pstore_record *record,
 static void pstore_dump(struct kmsg_dumper *dumper,
 			enum kmsg_dump_reason reason)
 {
+	struct kmsg_dump_iter iter;
 	unsigned long	total = 0;
 	const char	*why;
 	unsigned int	part = 1;
@@ -405,6 +406,8 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 		}
 	}

+	kmsg_dump_rewind(&iter);
+
 	oopscount++;
 	while (total < kmsg_bytes) {
 		char *dst;
@@ -435,7 +438,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 		dst_size -= header_size;

 		/* Write dump contents. */
-		if (!kmsg_dump_get_buffer(dumper, true, dst + header_size,
+		if (!kmsg_dump_get_buffer(&iter, true, dst + header_size,
 					  dst_size, &dump_size))
 			break;

--- a/include/linux/kmsg_dump.h
+++ b/include/linux/kmsg_dump.h
@@ -29,6 +29,16 @@ enum kmsg_dump_reason {
 	KMSG_DUMP_MAX
 };

+/**
+ * struct kmsg_dump_iter - iterator for retrieving kernel messages
+ * @cur_seq:	Points to the oldest message to dump
+ * @next_seq:	Points after the newest message to dump
+ */
+struct kmsg_dump_iter {
+	u64	cur_seq;
+	u64	next_seq;
+};
+
 /**
 * struct kmsg_dumper - kernel crash message dumper structure
 * @list:	Entry in the dumper list (private)
@@ -41,31 +51,19 @@ struct kmsg_dumper {
 	struct list_head list;
 	void (*dump)(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason);
 	enum kmsg_dump_reason max_reason;
-	bool active;
 	bool registered;
-
-	/* private state of the kmsg iterator */
-	u32 cur_idx;
-	u32 next_idx;
-	u64 cur_seq;
-	u64 next_seq;
 };

 #ifdef CONFIG_PRINTK
 void kmsg_dump(enum kmsg_dump_reason reason);

-bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
-			       char *line, size_t size, size_t *len);
-
-bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
+bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
 			char *line, size_t size, size_t *len);

-bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
-			  char *buf, size_t size, size_t *len);
+bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
+			  char *buf, size_t size, size_t *len_out);

-void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper);
-
-void kmsg_dump_rewind(struct kmsg_dumper *dumper);
+void kmsg_dump_rewind(struct kmsg_dump_iter *iter);

 int kmsg_dump_register(struct kmsg_dumper *dumper);

@@ -77,30 +75,19 @@ static inline void kmsg_dump(enum kmsg_dump_reason reason)
 {
 }

-static inline bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper,
-					     bool syslog, const char *line,
-					     size_t size, size_t *len)
-{
-	return false;
-}
-
-static inline bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
+static inline bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
 				const char *line, size_t size, size_t *len)
 {
 	return false;
 }

-static inline bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
+static inline bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
 					char *buf, size_t size, size_t *len)
 {
 	return false;
 }

-static inline void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
-{
-}
-
-static inline void kmsg_dump_rewind(struct kmsg_dumper *dumper)
+static inline void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
 {
 }

--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -2077,7 +2077,7 @@ static int kdb_dmesg(int argc, const char **argv)
 	int adjust = 0;
 	int n = 0;
 	int skip = 0;
-	struct kmsg_dumper dumper = { .active = 1 };
+	struct kmsg_dump_iter iter;
 	size_t len;
 	char buf[201];

@@ -2102,8 +2102,8 @@ static int kdb_dmesg(int argc, const char **argv)
 		kdb_set(2, setargs);
 	}

-	kmsg_dump_rewind_nolock(&dumper);
-	while (kmsg_dump_get_line_nolock(&dumper, 1, NULL, 0, NULL))
+	kmsg_dump_rewind(&iter);
+	while (kmsg_dump_get_line(&iter, 1, NULL, 0, NULL))
 		n++;

 	if (lines < 0) {
@@ -2135,8 +2135,8 @@ static int kdb_dmesg(int argc, const char **argv)
 	if (skip >= n || skip < 0)
 		return 0;

-	kmsg_dump_rewind_nolock(&dumper);
-	while (kmsg_dump_get_line_nolock(&dumper, 1, buf, sizeof(buf), &len)) {
+	kmsg_dump_rewind(&iter);
+	while (kmsg_dump_get_line(&iter, 1, buf, sizeof(buf), &len)) {
 		if (skip) {
 			skip--;
 			continue;
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -12,8 +12,6 @@

 #define PRINTK_NMI_CONTEXT_OFFSET	0x010000000

-extern raw_spinlock_t logbuf_lock;
-
 __printf(4, 0)
 int vprintk_store(int facility, int level,
 		  const struct dev_printk_info *dev_info,
@@ -21,7 +19,6 @@ int vprintk_store(int facility, int level,

 __printf(1, 0) int vprintk_default(const char *fmt, va_list args);
 __printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);
-__printf(1, 0) int vprintk_func(const char *fmt, va_list args);
 void __printk_safe_enter(void);
 void __printk_safe_exit(void);

@@ -56,10 +53,8 @@ void defer_console_output(void);

 #else

-__printf(1, 0) int vprintk_func(const char *fmt, va_list args) { return 0; }
-
 /*
- * In !PRINTK builds we still export logbuf_lock spin_lock, console_sem
+ * In !PRINTK builds we still export console_sem
 * semaphore and some of console functions (console_unlock()/etc.), so
 * printk-safe must preserve the existing local IRQ guarantees.
 */
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -16,7 +16,7 @@
 #include "internal.h"

 /*
- * printk() could not take logbuf_lock in NMI context. Instead,
+ * In NMI and safe mode, printk() avoids taking locks. Instead,
 * it uses an alternative implementation that temporary stores
 * the strings into a per-CPU buffer. The content of the buffer
 * is later flushed into the main ring buffer via IRQ work.
@@ -267,17 +267,9 @@ void printk_safe_flush(void)
 void printk_safe_flush_on_panic(void)
 {
 	/*
-	 * Make sure that we could access the main ring buffer.
+	 * Make sure that we could access the safe buffers.
 	 * Do not risk a double release when more CPUs are up.
 	 */
-	if (raw_spin_is_locked(&logbuf_lock)) {
-		if (num_online_cpus() > 1)
-			return;
-
-		debug_locks_off();
-		raw_spin_lock_init(&logbuf_lock);
-	}
-
 	if (raw_spin_is_locked(&safe_read_lock)) {
 		if (num_online_cpus() > 1)
 			return;
@@ -319,9 +311,7 @@ void noinstr printk_nmi_exit(void)
 * reordering.
 *
 * It has effect only when called in NMI context. Then printk()
- * will try to store the messages into the main logbuf directly
- * and use the per-CPU buffers only as a fallback when the lock
- * is not available.
+ * will store the messages into the main logbuf directly.
 */
 void printk_nmi_direct_enter(void)
 {
@@ -367,7 +357,7 @@ void __printk_safe_exit(void)
 	this_cpu_dec(printk_context);
 }

-__printf(1, 0) int vprintk_func(const char *fmt, va_list args)
+asmlinkage int vprintk(const char *fmt, va_list args)
 {
 #ifdef CONFIG_KGDB_KDB
 	/* Allow to pass printk() to kdb but avoid a recursion. */
@@ -376,20 +366,21 @@ __printf(1, 0) int vprintk_func(const char *fmt, va_list args)
 #endif

 	/*
-	 * Try to use the main logbuf even in NMI. But avoid calling console
+	 * Use the main logbuf even in NMI. But avoid calling console
 	 * drivers that might have their own locks.
 	 */
-	if ((this_cpu_read(printk_context) & PRINTK_NMI_DIRECT_CONTEXT_MASK) &&
-	    raw_spin_trylock(&logbuf_lock)) {
+	if ((this_cpu_read(printk_context) & PRINTK_NMI_DIRECT_CONTEXT_MASK)) {
+		unsigned long flags;
 		int len;

+		printk_safe_enter_irqsave(flags);
 		len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
-		raw_spin_unlock(&logbuf_lock);
+		printk_safe_exit_irqrestore(flags);
 		defer_console_output();
 		return len;
 	}

-	/* Use extra buffer in NMI when logbuf_lock is taken or in safe mode. */
+	/* Use extra buffer in NMI. */
 	if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK)
 		return vprintk_nmi(fmt, args);

@@ -420,3 +411,4 @@ void __init printk_safe_init(void)
 	/* Flush pending messages that did not have scheduled IRQ works. */
 	printk_safe_flush();
 }
+EXPORT_SYMBOL(vprintk);
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -577,24 +577,98 @@ netdev_features(void)
 {
 }

+struct page_flags_test {
+	int width;
+	int shift;
+	int mask;
+	unsigned long value;
+	const char *fmt;
+	const char *name;
+};
+
+static struct page_flags_test pft[] = {
+	{SECTIONS_WIDTH, SECTIONS_PGSHIFT, SECTIONS_MASK,
+	 0, "%d", "section"},
+	{NODES_WIDTH, NODES_PGSHIFT, NODES_MASK,
+	 0, "%d", "node"},
+	{ZONES_WIDTH, ZONES_PGSHIFT, ZONES_MASK,
+	 0, "%d", "zone"},
+	{LAST_CPUPID_WIDTH, LAST_CPUPID_PGSHIFT, LAST_CPUPID_MASK,
+	 0, "%#x", "lastcpupid"},
+	{KASAN_TAG_WIDTH, KASAN_TAG_PGSHIFT, KASAN_TAG_MASK,
+	 0, "%#x", "kasantag"},
+};
+
+static void __init
+page_flags_test(int section, int node, int zone, int last_cpupid,
+		int kasan_tag, int flags, const char *name, char *cmp_buf)
+{
+	unsigned long values[] = {section, node, zone, last_cpupid, kasan_tag};
+	unsigned long page_flags = 0;
+	unsigned long size = 0;
+	bool append = false;
+	int i;
+
+	flags &= BIT(NR_PAGEFLAGS) - 1;
+	if (flags) {
+		page_flags |= flags;
+		snprintf(cmp_buf + size, BUF_SIZE - size, "%s", name);
+		size = strlen(cmp_buf);
+#if SECTIONS_WIDTH || NODES_WIDTH || ZONES_WIDTH || \
+	LAST_CPUPID_WIDTH || KASAN_TAG_WIDTH
+		/* Other information also included in page flags */
+		snprintf(cmp_buf + size, BUF_SIZE - size, "|");
+		size = strlen(cmp_buf);
+#endif
+	}
+
+	/* Set the test value */
+	for (i = 0; i < ARRAY_SIZE(pft); i++)
+		pft[i].value = values[i];
+
+	for (i = 0; i < ARRAY_SIZE(pft); i++) {
+		if (!pft[i].width)
+			continue;
+
+		if (append) {
+			snprintf(cmp_buf + size, BUF_SIZE - size, "|");
+			size = strlen(cmp_buf);
+		}
+
+		page_flags |= (pft[i].value & pft[i].mask) << pft[i].shift;
+		snprintf(cmp_buf + size, BUF_SIZE - size, "%s=", pft[i].name);
+		size = strlen(cmp_buf);
+		snprintf(cmp_buf + size, BUF_SIZE - size, pft[i].fmt,
+			 pft[i].value & pft[i].mask);
+		size = strlen(cmp_buf);
+		append = true;
+	}
+
+	test(cmp_buf, "%pGp", &page_flags);
+}
+
 static void __init
 flags(void)
 {
 	unsigned long flags;
-	gfp_t gfp;
 	char *cmp_buffer;
+	gfp_t gfp;
+
+	cmp_buffer = kmalloc(BUF_SIZE, GFP_KERNEL);
+	if (!cmp_buffer)
+		return;

 	flags = 0;
-	test("", "%pGp", &flags);
+	page_flags_test(0, 0, 0, 0, 0, flags, "", cmp_buffer);

-	/* Page flags should filter the zone id */
 	flags = 1UL << NR_PAGEFLAGS;
-	test("", "%pGp", &flags);
+	page_flags_test(0, 0, 0, 0, 0, flags, "", cmp_buffer);

 	flags |= 1UL << PG_uptodate | 1UL << PG_dirty | 1UL << PG_lru
 		| 1UL << PG_active | 1UL << PG_swapbacked;
-	test("uptodate|dirty|lru|active|swapbacked", "%pGp", &flags);
-
+	page_flags_test(1, 1, 1, 0x1fffff, 1, flags,
+			"uptodate|dirty|lru|active|swapbacked",
+			cmp_buffer);

 	flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC
 			| VM_DENYWRITE;
@@ -609,10 +683,6 @@ flags(void)
 	gfp = __GFP_ATOMIC;
 	test("__GFP_ATOMIC", "%pGg", &gfp);

-	cmp_buffer = kmalloc(BUF_SIZE, GFP_KERNEL);
-	if (!cmp_buffer)
-		return;
-
 	/* Any flags not translated by the table should remain numeric */
 	gfp = ~__GFP_BITS_MASK;
 	snprintf(cmp_buffer, BUF_SIZE, "%#lx", (unsigned long) gfp);
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1916,6 +1916,66 @@ char *format_flags(char *buf, char *end, unsigned long flags,
 	return buf;
 }

+struct page_flags_fields {
+	int width;
+	int shift;
+	int mask;
+	const struct printf_spec *spec;
+	const char *name;
+};
+
+static const struct page_flags_fields pff[] = {
+	{SECTIONS_WIDTH, SECTIONS_PGSHIFT, SECTIONS_MASK,
+	 &default_dec_spec, "section"},
+	{NODES_WIDTH, NODES_PGSHIFT, NODES_MASK,
+	 &default_dec_spec, "node"},
+	{ZONES_WIDTH, ZONES_PGSHIFT, ZONES_MASK,
+	 &default_dec_spec, "zone"},
+	{LAST_CPUPID_WIDTH, LAST_CPUPID_PGSHIFT, LAST_CPUPID_MASK,
+	 &default_flag_spec, "lastcpupid"},
+	{KASAN_TAG_WIDTH, KASAN_TAG_PGSHIFT, KASAN_TAG_MASK,
+	 &default_flag_spec, "kasantag"},
+};
+
+static
+char *format_page_flags(char *buf, char *end, unsigned long flags)
+{
+	unsigned long main_flags = flags & (BIT(NR_PAGEFLAGS) - 1);
+	bool append = false;
+	int i;
+
+	/* Page flags from the main area. */
+	if (main_flags) {
+		buf = format_flags(buf, end, main_flags, pageflag_names);
+		append = true;
+	}
+
+	/* Page flags from the fields area */
+	for (i = 0; i < ARRAY_SIZE(pff); i++) {
+		/* Skip undefined fields. */
+		if (!pff[i].width)
+			continue;
+
+		/* Format: Flag Name + '=' (equals sign) + Number + '|' (separator) */
+		if (append) {
+			if (buf < end)
+				*buf = '|';
+			buf++;
+		}
+
+		buf = string(buf, end, pff[i].name, default_str_spec);
+		if (buf < end)
+			*buf = '=';
+		buf++;
+		buf = number(buf, end, (flags >> pff[i].shift) & pff[i].mask,
+			     *pff[i].spec);
+
+		append = true;
+	}
+
+	return buf;
+}
+
 static noinline_for_stack
 char *flags_string(char *buf, char *end, void *flags_ptr,
 		   struct printf_spec spec, const char *fmt)
@@ -1928,11 +1988,7 @@ char *flags_string(char *buf, char *end, void *flags_ptr,

 	switch (fmt[1]) {
 	case 'p':
-		flags = *(unsigned long *)flags_ptr;
-		/* Remove zone id */
-		flags &= (1UL << NR_PAGEFLAGS) - 1;
-		names = pageflag_names;
-		break;
+		return format_page_flags(buf, end, *(unsigned long *)flags_ptr);
 	case 'v':
 		flags = *(unsigned long *)flags_ptr;
 		names = vmaflag_names;
@@ -2096,6 +2152,9 @@ EXPORT_SYMBOL_GPL(no_hash_pointers);

 static int __init no_hash_pointers_enable(char *str)
 {
+	if (no_hash_pointers)
+		return 0;
+
 	no_hash_pointers = true;

 	pr_warn("**********************************************************\n");
@@ -2186,7 +2245,9 @@ early_param("no_hash_pointers", no_hash_pointers_enable);
 *       Implements a "recursive vsnprintf".
 *       Do not use this feature without some mechanism to verify the
 *       correctness of the format string and va_list arguments.
- * - 'K' For a kernel pointer that should be hidden from unprivileged users
+ * - 'K' For a kernel pointer that should be hidden from unprivileged users.
+ *       Use only for procfs, sysfs and similar files, not printk(); please
+ *       read the documentation (path below) first.
 * - 'NF' For a netdev_features_t
 * - 'h[CDN]' For a variable-length buffer, it prints it as a hex string with
 *            a certain separator (' ' by default):
@@ -2225,7 +2286,8 @@ early_param("no_hash_pointers", no_hash_pointers_enable);
 *		Without an option prints the full name of the node
 *		f full name
 *		P node name, including a possible unit address
- * - 'x' For printing the address. Equivalent to "%lx".
+ * - 'x' For printing the address unmodified. Equivalent to "%lx".
+ *       Please read the documentation (path below) before using!
 * - '[ku]s' For a BPF/tracing related format specifier, e.g. used out of
 *           bpf_trace_printk() where [ku] prefix specifies either kernel (k)
 *           or user (u) memory to probe, and:
@@ -3135,8 +3197,6 @@ int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf)
 			switch (*fmt) {
 			case 'S':
 			case 's':
-			case 'F':
-			case 'f':
 			case 'x':
 			case 'K':
 			case 'e':
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -624,7 +624,7 @@ static void print_track(const char *s, struct track *t, unsigned long pr_time)
 	if (!t->addr)
 		return;

-	pr_err("INFO: %s in %pS age=%lu cpu=%u pid=%d\n",
+	pr_err("%s in %pS age=%lu cpu=%u pid=%d\n",
 	       s, (void *)t->addr, pr_time - t->when, t->cpu, t->pid);
 #ifdef CONFIG_STACKTRACE
 	{
@@ -650,8 +650,9 @@ void print_tracking(struct kmem_cache *s, void *object)

 static void print_page_info(struct page *page)
 {
-	pr_err("INFO: Slab 0x%p objects=%u used=%u fp=0x%p flags=0x%04lx\n",
-	       page, page->objects, page->inuse, page->freelist, page->flags);
+	pr_err("Slab 0x%p objects=%u used=%u fp=0x%p flags=%#lx(%pGp)\n",
+	       page, page->objects, page->inuse, page->freelist,
+	       page->flags, &page->flags);

 }

@@ -706,7 +707,7 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)

 	print_page_info(page);

-	pr_err("INFO: Object 0x%p @offset=%tu fp=0x%p\n\n",
+	pr_err("Object 0x%p @offset=%tu fp=0x%p\n\n",
 	       p, p - addr, get_freepointer(s, p));

 	if (s->flags & SLAB_RED_ZONE)
@@ -799,7 +800,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
 		end--;

 	slab_bug(s, "%s overwritten", what);
-	pr_err("INFO: 0x%p-0x%p @offset=%tu. First byte 0x%x instead of 0x%x\n",
+	pr_err("0x%p-0x%p @offset=%tu. First byte 0x%x instead of 0x%x\n",
 					fault, end - 1, fault - addr,
 					fault[0], value);
 	print_trailer(s, page, object);
@@ -3898,7 +3899,7 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page,
 	for_each_object(p, s, addr, page->objects) {

 		if (!test_bit(__obj_to_index(s, addr, p), map)) {
-			pr_err("INFO: Object 0x%p @offset=%tu\n", p, p - addr);
+			pr_err("Object 0x%p @offset=%tu\n", p, p - addr);
 			print_tracking(s, p);
 		}
 	}