diff options
| -rw-r--r-- | Documentation/core-api/printk-formats.rst | 28 | ||||
| -rw-r--r-- | MAINTAINERS | 8 | ||||
| -rw-r--r-- | lib/test_printf.c | 90 | ||||
| -rw-r--r-- | lib/vsprintf.c | 78 | ||||
| -rw-r--r-- | mm/slub.c | 13 |
5 files changed, 186 insertions, 31 deletions
diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index 160e710d992f..9be6de402cb9 100644 --- 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 diff --git a/MAINTAINERS b/MAINTAINERS index a9efff1a18c6..e626953f5ed8 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -14319,7 +14319,7 @@ 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 @@ -19156,7 +19156,7 @@ 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 @@ -19807,7 +19807,7 @@ 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 @@ -19821,7 +19821,7 @@ 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 diff --git a/lib/test_printf.c b/lib/test_printf.c index 95a2f82427c7..27b964ec723d 100644 --- 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); diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 41ddc353ebb8..6c56c62fd9a5 100644 --- 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': diff --git a/mm/slub.c b/mm/slub.c index f5baf429654f..5eb120fdde8b 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -615,7 +615,7 @@ 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 { @@ -641,8 +641,9 @@ 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); } @@ -697,7 +698,7 @@ 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) @@ -790,7 +791,7 @@ 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); @@ -3868,7 +3869,7 @@ 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); } } |