From: Marco Elver elver@google.com
mainline inclusion from mainline-v5.12-rc1 commit 35beccf0926d42ee0d56e41979ec8cdf814c4769 category: feature bugzilla: 181005 https://gitee.com/openeuler/kernel/issues/I4EUY7
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
-----------------------------------------------
We cannot rely on CONFIG_DEBUG_KERNEL to decide if we're running a "debug kernel" where we can safely show potentially sensitive information in the kernel log.
Instead, simply rely on the newly introduced "no_hash_pointers" to print unhashed kernel pointers, as well as decide if our reports can include other potentially sensitive information such as registers and corrupted bytes.
Link: https://lkml.kernel.org/r/20210223082043.1972742-1-elver@google.com Signed-off-by: Marco Elver elver@google.com Cc: Timur Tabi timur@kernel.org Cc: Alexander Potapenko glider@google.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Andrey Konovalov andreyknvl@google.com Cc: Jann Horn jannh@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [Peng Liu: dependent on 5ead723a20e0447bc7db33dc3070b420e5f80aa6] Signed-off-by: Peng Liu liupeng256@huawei.com Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com
Signed-off-by: Chen Jun chenjun102@huawei.com --- Documentation/dev-tools/kfence.rst | 8 ++++---- mm/kfence/core.c | 10 +++------- mm/kfence/kfence.h | 7 ------- mm/kfence/kfence_test.c | 2 +- mm/kfence/report.c | 18 ++++++++++-------- 5 files changed, 18 insertions(+), 27 deletions(-)
diff --git a/Documentation/dev-tools/kfence.rst b/Documentation/dev-tools/kfence.rst index 58a0a5fa1ddc..fdf04e741ea5 100644 --- a/Documentation/dev-tools/kfence.rst +++ b/Documentation/dev-tools/kfence.rst @@ -88,8 +88,8 @@ A typical out-of-bounds access looks like this::
The header of the report provides a short summary of the function involved in the access. It is followed by more detailed information about the access and -its origin. Note that, real kernel addresses are only shown for -``CONFIG_DEBUG_KERNEL=y`` builds. +its origin. Note that, real kernel addresses are only shown when using the +kernel command line option ``no_hash_pointers``.
Use-after-free accesses are reported as::
@@ -184,8 +184,8 @@ invalidly written bytes (offset from the address) are shown; in this representation, '.' denote untouched bytes. In the example above ``0xac`` is the value written to the invalid address at offset 0, and the remaining '.' denote that no following bytes have been touched. Note that, real values are -only shown for ``CONFIG_DEBUG_KERNEL=y`` builds; to avoid information -disclosure for non-debug builds, '!' is used instead to denote invalidly +only shown if the kernel was booted with ``no_hash_pointers``; to avoid +information disclosure otherwise, '!' is used instead to denote invalidly written bytes.
And finally, KFENCE may also report on invalid accesses to any protected page diff --git a/mm/kfence/core.c b/mm/kfence/core.c index cfe3d32ac5b7..3b8ec938470a 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -646,13 +646,9 @@ void __init kfence_init(void)
WRITE_ONCE(kfence_enabled, true); schedule_delayed_work(&kfence_timer, 0); - pr_info("initialized - using %lu bytes for %d objects", KFENCE_POOL_SIZE, - CONFIG_KFENCE_NUM_OBJECTS); - if (IS_ENABLED(CONFIG_DEBUG_KERNEL)) - pr_cont(" at 0x%px-0x%px\n", (void *)__kfence_pool, - (void *)(__kfence_pool + KFENCE_POOL_SIZE)); - else - pr_cont("\n"); + pr_info("initialized - using %lu bytes for %d objects at 0x%p-0x%p\n", KFENCE_POOL_SIZE, + CONFIG_KFENCE_NUM_OBJECTS, (void *)__kfence_pool, + (void *)(__kfence_pool + KFENCE_POOL_SIZE)); }
void kfence_shutdown_cache(struct kmem_cache *s) diff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h index 1accc840dbbe..24065321ff8a 100644 --- a/mm/kfence/kfence.h +++ b/mm/kfence/kfence.h @@ -16,13 +16,6 @@
#include "../slab.h" /* for struct kmem_cache */
-/* For non-debug builds, avoid leaking kernel pointers into dmesg. */ -#ifdef CONFIG_DEBUG_KERNEL -#define PTR_FMT "%px" -#else -#define PTR_FMT "%p" -#endif - /* * Get the canary byte pattern for @addr. Use a pattern that varies based on the * lower 3 bits of the address, to detect memory corruptions with higher diff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c index db1bb596acaf..4acf4251ee04 100644 --- a/mm/kfence/kfence_test.c +++ b/mm/kfence/kfence_test.c @@ -146,7 +146,7 @@ static bool report_matches(const struct expect_report *r) break; }
- cur += scnprintf(cur, end - cur, " 0x" PTR_FMT, (void *)r->addr); + cur += scnprintf(cur, end - cur, " 0x%p", (void *)r->addr);
spin_lock_irqsave(&observed.lock, flags); if (!report_available()) diff --git a/mm/kfence/report.c b/mm/kfence/report.c index 901bd7ee83d8..4a424de44e2d 100644 --- a/mm/kfence/report.c +++ b/mm/kfence/report.c @@ -19,6 +19,8 @@
#include "kfence.h"
+extern bool no_hash_pointers; + /* Helper function to either print to a seq_file or to console. */ __printf(2, 3) static void seq_con_printf(struct seq_file *seq, const char *fmt, ...) @@ -118,7 +120,7 @@ void kfence_print_object(struct seq_file *seq, const struct kfence_metadata *met }
seq_con_printf(seq, - "kfence-#%zd [0x" PTR_FMT "-0x" PTR_FMT + "kfence-#%zd [0x%p-0x%p" ", size=%d, cache=%s] allocated by task %d:\n", meta - kfence_metadata, (void *)start, (void *)(start + size - 1), size, (cache && cache->name) ? cache->name : "<destroyed>", meta->alloc_track.pid); @@ -148,7 +150,7 @@ static void print_diff_canary(unsigned long address, size_t bytes_to_show, for (cur = (const u8 *)address; cur < end; cur++) { if (*cur == KFENCE_CANARY_PATTERN(cur)) pr_cont(" ."); - else if (IS_ENABLED(CONFIG_DEBUG_KERNEL)) + else if (no_hash_pointers) pr_cont(" 0x%02x", *cur); else /* Do not leak kernel memory in non-debug builds. */ pr_cont(" !"); @@ -201,7 +203,7 @@ void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *r
pr_err("BUG: KFENCE: out-of-bounds %s in %pS\n\n", get_access_type(is_write), (void *)stack_entries[skipnr]); - pr_err("Out-of-bounds %s at 0x" PTR_FMT " (%luB %s of kfence-#%zd):\n", + pr_err("Out-of-bounds %s at 0x%p (%luB %s of kfence-#%zd):\n", get_access_type(is_write), (void *)address, left_of_object ? meta->addr - address : address - meta->addr, left_of_object ? "left" : "right", object_index); @@ -210,24 +212,24 @@ void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *r case KFENCE_ERROR_UAF: pr_err("BUG: KFENCE: use-after-free %s in %pS\n\n", get_access_type(is_write), (void *)stack_entries[skipnr]); - pr_err("Use-after-free %s at 0x" PTR_FMT " (in kfence-#%zd):\n", + pr_err("Use-after-free %s at 0x%p (in kfence-#%zd):\n", get_access_type(is_write), (void *)address, object_index); break; case KFENCE_ERROR_CORRUPTION: pr_err("BUG: KFENCE: memory corruption in %pS\n\n", (void *)stack_entries[skipnr]); - pr_err("Corrupted memory at 0x" PTR_FMT " ", (void *)address); + pr_err("Corrupted memory at 0x%p ", (void *)address); print_diff_canary(address, 16, meta); pr_cont(" (in kfence-#%zd):\n", object_index); break; case KFENCE_ERROR_INVALID: pr_err("BUG: KFENCE: invalid %s in %pS\n\n", get_access_type(is_write), (void *)stack_entries[skipnr]); - pr_err("Invalid %s at 0x" PTR_FMT ":\n", get_access_type(is_write), + pr_err("Invalid %s at 0x%p:\n", get_access_type(is_write), (void *)address); break; case KFENCE_ERROR_INVALID_FREE: pr_err("BUG: KFENCE: invalid free in %pS\n\n", (void *)stack_entries[skipnr]); - pr_err("Invalid free of 0x" PTR_FMT " (in kfence-#%zd):\n", (void *)address, + pr_err("Invalid free of 0x%p (in kfence-#%zd):\n", (void *)address, object_index); break; } @@ -242,7 +244,7 @@ void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *r
/* Print report footer. */ pr_err("\n"); - if (IS_ENABLED(CONFIG_DEBUG_KERNEL) && regs) + if (no_hash_pointers && regs) show_regs(regs); else dump_stack_print_info(KERN_ERR);