[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <fc6396c21f8a9fa83166fd4ccaee7c2c5069f0b2.camel@gmail.com>
Date: Tue, 08 Oct 2024 02:41:01 -0700
From: Eduard Zingerman <eddyz87@...il.com>
To: feng.tang@...el.com
Cc: syzbot <syzbot+7e46cdef14bf496a3ab4@...kaller.appspotmail.com>,
42.hyeyoo@...il.com, akpm@...ux-foundation.org, andrii@...nel.org,
ast@...nel.org, bpf@...r.kernel.org, cl@...ux.com, daniel@...earbox.net,
haoluo@...gle.com, iamjoonsoo.kim@....com, john.fastabend@...il.com,
jolsa@...nel.org, kpsingh@...nel.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, martin.lau@...ux.dev, penberg@...nel.org,
rientjes@...gle.com, roman.gushchin@...ux.dev, sdf@...ichev.me,
song@...nel.org, syzkaller-bugs@...glegroups.com, vbabka@...e.cz,
yonghong.song@...ux.dev
Subject: Re: [syzbot] [bpf?] WARNING in push_jmp_history
On Tue, 2024-10-08 at 01:43 -0700, syzbot wrote:
> syzbot has bisected this issue to:
>
> commit d0a38fad51cc70ab3dd3c59b54d8079ac19220b9
> Author: Feng Tang <feng.tang@...el.com>
> Date: Wed Sep 11 06:45:34 2024 +0000
>
> mm/slub: Improve redzone check and zeroing for krealloc()
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11ddbb80580000
> start commit: c02d24a5af66 Add linux-next specific files for 20241003
> git tree: linux-next
> final oops: https://syzkaller.appspot.com/x/report.txt?x=13ddbb80580000
> console output: https://syzkaller.appspot.com/x/log.txt?x=15ddbb80580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=94f9caf16c0af42d
> dashboard link: https://syzkaller.appspot.com/bug?extid=7e46cdef14bf496a3ab4
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10b82707980000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16f4c327980000
>
> Reported-by: syzbot+7e46cdef14bf496a3ab4@...kaller.appspotmail.com
> Fixes: d0a38fad51cc ("mm/slub: Improve redzone check and zeroing for krealloc()")
>
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
There are two issues demonstrated by this repro:
- one is mm/slub related;
- another one is verification taking forever.
About the mm/slub related. Applying the following patch with
additional logging on top of commit d0a38fad51cc identified by syzbot:
------- 8< ------------------------------------------------------------
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9a7ed527e47e..c1582a6d1d33 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3494,7 +3494,9 @@ static int push_jmp_history(struct bpf_verifier_env *env, struct bpf_verifier_st
cnt++;
alloc_size = kmalloc_size_roundup(size_mul(cnt, sizeof(*p)));
+ printk("push_jmp_history: #1 cur->jmp_history=%p\n", cur->jmp_history);
p = krealloc(cur->jmp_history, alloc_size, GFP_USER);
+ printk("push_jmp_history: #2 cur->jmp_history=%p\n", p);
if (!p)
return -ENOMEM;
cur->jmp_history = p;
diff --git a/mm/slub.c b/mm/slub.c
index e0fb0a26c796..3f5b080ac1f5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4627,7 +4627,7 @@ static inline struct kmem_cache *virt_to_cache(const void *obj)
struct slab *slab;
slab = virt_to_slab(obj);
- if (WARN_ONCE(!slab, "%s: Object is not a Slab page!\n", __func__))
+ if (WARN_ONCE(!slab, "%s: Object %p is not a Slab page!\n", __func__, obj))
return NULL;
return slab->slab_cache;
}
------------------------------------------------------------ >8 -------
Produces the following log:
l1: [ 2.942120] push_jmp_history: #2 cur->jmp_history=00000000a0f6f503
l2: [ 2.944445] push_jmp_history: #1 cur->jmp_history=00000000a0f6f503
l3: [ 2.944560] ------------[ cut here ]------------
l4: [ 2.944647] virt_to_cache: Object 00000000a0f6f503 is not a Slab page!
l5: [ 2.944765] WARNING: CPU: 0 PID: 145 at mm/slub.c:4630 krealloc_noprof (mm/slub.c:4630 mm/slub.c:4728 mm/slub.c:4813)
l6: [ 2.944906] Modules linked in:
l7: [ 2.945134] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-2.fc40 04/01/2014
l8: [ 2.945285] RIP: 0010:krealloc_noprof (mm/slub.c:4630 mm/slub.c:4728 mm/slub.c:4813)
...
l9: [ 2.952088] BUG: kernel NULL pointer dereference, address: 000000000000001c
l10: [ 2.952171] #PF: supervisor read access in kernel mode
l11: [ 2.952240] #PF: error_code(0x0000) - not-present page
l12: [ 2.952309] PGD 105d51067 P4D 105d51067 PUD 1013d0067 PMD 0
l13: [ 2.952402] Oops: Oops: 0000 [#1] PREEMPT SMP KASAN NOPTI
l14: [ 2.952611] Tainted: [W]=WARN
l15: [ 2.952664] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-2.fc40 04/01/2014
l16: [ 2.952794] RIP: 0010:krealloc_noprof (mm/slub.c:0 mm/slub.c:4729 mm/slub.c:4813)
Lines l{1,2,4} show that address 0xa0f6f503 was first allocated by
krealloc and then krealloc failed to recognize it as such.
The warning at l3 is reported by virt_to_cache() called from
__do_krealloc():
4715 static __always_inline __realloc_size(2) void *
4716 __do_krealloc(const void *p, size_t new_size, gfp_t flags)
4717 {
4718 void *ret;
4719 size_t ks;
4720 int orig_size = 0;
4721 struct kmem_cache *s;
4722
4723 /* Check for double-free. */
4724 if (likely(!ZERO_OR_NULL_PTR(p))) {
4725 if (!kasan_check_byte(p))
4726 return NULL;
4727
4728 s = virt_to_cache(p);
4729 orig_size = get_orig_size(s, (void *)p);
4730 ks = s->object_size;
When virt_to_cache() reports the warning it returns NULL.
Hence variable 's' at line 4728 is NULL and this causes null pointer
dereference at line 4730, reported at l9.
Lines 4725-4730 were changed by commit d0a38fad51cc identified by syzbot,
previously 'ks' was identified using other means.
Feng, this issue seem unrelated to BPF verifier, could you please take a look?
Best regards,
Eduard
Powered by blists - more mailing lists