On 11/28, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: c35bd4e42885 Add linux-next specific files for 20221124
> git tree: linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=13369dc5880000
> kernel config: https://syzkaller.appspot.com/x/.config?x=11e19c740a0b2926
> dashboard link: https://syzkaller.appspot.com/bug?extid=b1e1f7feb407b56d0355
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1345a205880000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=124c644b880000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/968fee464d14/disk-c35bd4e4.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/4f46fe801b5b/vmlinux-c35bd4e4.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/c2cdf8fb264e/bzImage-c35bd4e4.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b1e1f7feb407b56d0355@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in copy_array+0x96/0x100 kernel/bpf/verifier.c:1032
> Write of size 232 at addr ffff88801ed62600 by task syz-executor990/5290
>
> CPU: 0 PID: 5290 Comm: syz-executor990 Not tainted 6.1.0-rc6-next-20221124-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
> print_address_description mm/kasan/report.c:253 [inline]
> print_report+0x15e/0x45d mm/kasan/report.c:364
> kasan_report+0xbf/0x1f0 mm/kasan/report.c:464
> check_region_inline mm/kasan/generic.c:183 [inline]
> kasan_check_range+0x141/0x190 mm/kasan/generic.c:189
> memcpy+0x3d/0x60 mm/kasan/shadow.c:66
> copy_array+0x96/0x100 kernel/bpf/verifier.c:1032
> copy_verifier_state+0xa9/0xbe0 kernel/bpf/verifier.c:1210
> pop_stack+0x8c/0x2f0 kernel/bpf/verifier.c:1273
> do_check kernel/bpf/verifier.c:13733 [inline]
> do_check_common+0x372b/0xc5e0 kernel/bpf/verifier.c:15991
> do_check_main kernel/bpf/verifier.c:16054 [inline]
> bpf_check+0x7371/0xad00 kernel/bpf/verifier.c:16624
> bpf_prog_load+0x1543/0x2230 kernel/bpf/syscall.c:2619
> __sys_bpf+0x1436/0x4ff0 kernel/bpf/syscall.c:4979
> __do_sys_bpf kernel/bpf/syscall.c:5083 [inline]
> __se_sys_bpf kernel/bpf/syscall.c:5081 [inline]
> __x64_sys_bpf+0x79/0xc0 kernel/bpf/syscall.c:5081
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7fc18e7bbc29
> Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffd8f27a968 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fc18e7bbc29
> RDX: 0000000000000048 RSI: 0000000020000200 RDI: 0000000000000005
> RBP: 00007fc18e77fdd0 R08: 0000000000000000 R09: 0000000000000000
> R10: 00000000ffffffff R11: 0000000000000246 R12: 00007fc18e77fe60
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> </TASK>
>
> Allocated by task 5290:
> kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
> kasan_set_track+0x25/0x30 mm/kasan/common.c:52
> ____kasan_kmalloc mm/kasan/common.c:376 [inline]
> ____kasan_kmalloc mm/kasan/common.c:335 [inline]
> __kasan_krealloc+0x145/0x180 mm/kasan/common.c:444
> kasan_krealloc include/linux/kasan.h:232 [inline]
> __do_krealloc mm/slab_common.c:1348 [inline]
> krealloc+0xa8/0x100 mm/slab_common.c:1385
> push_jmp_history+0x89/0x260 kernel/bpf/verifier.c:2528
> is_state_visited kernel/bpf/verifier.c:13269 [inline]
> do_check kernel/bpf/verifier.c:13466 [inline]
> do_check_common+0x4b47/0xc5e0 kernel/bpf/verifier.c:15991
> do_check_main kernel/bpf/verifier.c:16054 [inline]
> bpf_check+0x7371/0xad00 kernel/bpf/verifier.c:16624
> bpf_prog_load+0x1543/0x2230 kernel/bpf/syscall.c:2619
> __sys_bpf+0x1436/0x4ff0 kernel/bpf/syscall.c:4979
> __do_sys_bpf kernel/bpf/syscall.c:5083 [inline]
> __se_sys_bpf kernel/bpf/syscall.c:5081 [inline]
> __x64_sys_bpf+0x79/0xc0 kernel/bpf/syscall.c:5081
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> The buggy address belongs to the object at ffff88801ed62600
> which belongs to the cache kmalloc-256 of size 256
> The buggy address is located 0 bytes inside of
> 256-byte region [ffff88801ed62600, ffff88801ed62700)
>
> The buggy address belongs to the physical page:
> page:ffffea00007b5880 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1ed62
> head:ffffea00007b5880 order:1 compound_mapcount:0 subpages_mapcount:0 compound_pincount:0
> flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
> raw: 00fff00000010200 ffff888012441b40 ffffea0000809f80 dead000000000002
> raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 56, tgid 56 (kworker/u4:4), ts 7761288109, free_ts 0
> prep_new_page mm/page_alloc.c:2541 [inline]
> get_page_from_freelist+0x119c/0x2cd0 mm/page_alloc.c:4293
> __alloc_pages+0x1cb/0x5b0 mm/page_alloc.c:5551
> alloc_pages+0x1aa/0x270 mm/mempolicy.c:2285
> alloc_slab_page mm/slub.c:1833 [inline]
> allocate_slab+0x25e/0x350 mm/slub.c:1980
> new_slab mm/slub.c:2033 [inline]
> ___slab_alloc+0xa91/0x1400 mm/slub.c:3211
> __slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3310
> slab_alloc_node mm/slub.c:3395 [inline]
> __kmem_cache_alloc_node+0x1a9/0x430 mm/slub.c:3472
> kmalloc_trace+0x26/0x60 mm/slab_common.c:1049
> kmalloc include/linux/slab.h:571 [inline]
> scsi_probe_and_add_lun+0x3ae/0x34d0 drivers/scsi/scsi_scan.c:1186
> __scsi_scan_target+0x21f/0xda0 drivers/scsi/scsi_scan.c:1664
> scsi_scan_channel drivers/scsi/scsi_scan.c:1752 [inline]
> scsi_scan_channel+0x148/0x1e0 drivers/scsi/scsi_scan.c:1728
> scsi_scan_host_selected+0x2e3/0x3b0 drivers/scsi/scsi_scan.c:1781
> do_scsi_scan_host+0x1e8/0x260 drivers/scsi/scsi_scan.c:1920
> do_scan_async+0x42/0x500 drivers/scsi/scsi_scan.c:1930
> async_run_entry_fn+0x9c/0x530 kernel/async.c:127
> process_one_work+0x9bf/0x1710 kernel/workqueue.c:2289
> page_owner free stack trace missing
>
> Memory state around the buggy address:
> ffff88801ed62500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88801ed62580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >ffff88801ed62600: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
> ^
> ffff88801ed62680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88801ed62700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches
#syz test
commit 589aa8077dcf413b06c78c6d8095496c98720c25
Author: Stanislav Fomichev <sdf@xxxxxxxxxx>
AuthorDate: Tue Dec 20 11:51:17 2022 -0800
Commit: Stanislav Fomichev <sdf@xxxxxxxxxx>
CommitDate: Tue Dec 20 11:51:17 2022 -0800
Revert "mm: Make ksize() a reporting-only function"
This reverts commit 38931d8989b5760b0bd17c9ec99e81986258e4cb.
diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index 73684642c42d..0d59098f0876 100644
--- a/mm/kasan/kasan_test.c
+++ b/mm/kasan/kasan_test.c
@@ -783,30 +783,23 @@ static void kasan_global_oob_left(struct kunit *test)
KUNIT_EXPECT_KASAN_FAIL(test, *(volatile char *)p);
}
-/* Check that ksize() does NOT unpoison whole object. */
+/* Check that ksize() makes the whole object accessible. */
static void ksize_unpoisons_memory(struct kunit *test)
{
char *ptr;
- size_t size = 128 - KASAN_GRANULE_SIZE - 5;
- size_t real_size;
+ size_t size = 123, real_size;
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
-
real_size = ksize(ptr);
- KUNIT_EXPECT_GT(test, real_size, size);
OPTIMIZER_HIDE_VAR(ptr);
- /* These accesses shouldn't trigger a KASAN report. */
- ptr[0] = 'x';
- ptr[size - 1] = 'x';
+ /* This access shouldn't trigger a KASAN report. */
+ ptr[size] = 'x';
- /* These must trigger a KASAN report. */
- if (IS_ENABLED(CONFIG_KASAN_GENERIC))
- KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[size]);
- KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[size + 5]);
- KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[real_size - 1]);
+ /* This one must. */
+ KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[real_size]);
kfree(ptr);
}
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 7e96abf1bd7d..33b1886b06eb 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1333,11 +1333,11 @@ __do_krealloc(const void *p, size_t new_size, gfp_t flags)
void *ret;
size_t ks;
- /* Check for double-free before calling ksize. */
+ /* Don't use instrumented ksize to allow precise KASAN poisoning. */
if (likely(!ZERO_OR_NULL_PTR(p))) {
if (!kasan_check_byte(p))
return NULL;
- ks = ksize(p);
+ ks = kfence_ksize(p) ?: __ksize(p);
} else
ks = 0;
@@ -1405,10 +1405,8 @@ void kfree_sensitive(const void *p)
void *mem = (void *)p;
ks = ksize(mem);
- if (ks) {
- kasan_unpoison_range(mem, ks);
+ if (ks)
memzero_explicit(mem, ks);
- }
kfree(mem);
}
EXPORT_SYMBOL(kfree_sensitive);
@@ -1429,11 +1427,13 @@ EXPORT_SYMBOL(kfree_sensitive);
*/
size_t ksize(const void *objp)
{
+ size_t size;
+
/*
- * We need to first check that the pointer to the object is valid.
- * The KASAN report printed from ksize() is more useful, then when
- * it's printed later when the behaviour could be undefined due to
- * a potential use-after-free or double-free.
+ * We need to first check that the pointer to the object is valid, and
+ * only then unpoison the memory. The report printed from ksize() is
+ * more useful, then when it's printed later when the behaviour could
+ * be undefined due to a potential use-after-free or double-free.
*
* We use kasan_check_byte(), which is supported for the hardware
* tag-based KASAN mode, unlike kasan_check_read/write().
@@ -1447,7 +1447,13 @@ size_t ksize(const void *objp)
if (unlikely(ZERO_OR_NULL_PTR(objp)) || !kasan_check_byte(objp))
return 0;
- return kfence_ksize(objp) ?: __ksize(objp);
+ size = kfence_ksize(objp) ?: __ksize(objp);
+ /*
+ * We assume that ksize callers could use whole allocated area,
+ * so we need to unpoison this area.
+ */
+ kasan_unpoison_range(objp, size);
+ return size;
}
EXPORT_SYMBOL(ksize);
