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Fri, 18 Oct 2024 10:30:23 -0700 (PDT) MIME-Version: 1.0 References: <20241018152925.138341-1-hao.ge@linux.dev> <20241018162559.143548-1-hao.ge@linux.dev> In-Reply-To: <20241018162559.143548-1-hao.ge@linux.dev> From: Suren Baghdasaryan Date: Fri, 18 Oct 2024 10:30:12 -0700 Message-ID: Subject: Re: [PATCH v2] mm/codetag: move ref and tag null pointer check to alloc_tag_add To: Hao Ge Cc: kent.overstreet@linux.dev, akpm@linux-foundation.org, yuzhao@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hao Ge Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 8BCFFC0019 X-Stat-Signature: mfmq8xfzzgiqn3xoshb1qwpurk6khzc7 X-HE-Tag: 1729272611-135379 X-HE-Meta: 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 y1cRUmDW YBHeeGp6QQC9BrcqPdnDY0uQROYTaLFKrBgvF1ZSOG9NEPMs/0Cg5NgQmtIi7U6E2yE/2nRVzWDA2DyjI2qp6Ibv8RYV1yjCd/N6bks5cd0P9kTjECYUSWzn3cxm5Lhtju6d3a0AFwVkCaUHMQIfpX7KZPfjQAdwPzQcxfga0xSN5nY7bc/E6YOAmqn8cyZy8ZXqXAO7ooLQVhg4jr73u8dkRrXngGnhQmfAY04IYXJX83z8= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Oct 18, 2024 at 9:26=E2=80=AFAM Hao Ge wrote: > > From: Hao Ge > > When we compile and load lib/slub_kunit.c,it will cause a panic. > > The root cause is that __kmalloc_cache_noprof was directly called > instead of kmem_cache_alloc,which resulted in no alloc_tag being > allocated.This caused current->alloc_tag to be null,leading to a > null pointer dereference in alloc_tag_ref_set. > > Despite the fact that my colleague Pei Xiao will later fix the code > in slub_kunit.c,we still need to move the null pointer check for ref > and tag to alloc_tag_add here. > It is sufficient for us to issue a warning to the user; > It should not lead to a panic. > > Here is the log for the panic: > > [ 74.779373][ T2158] Unable to handle kernel NULL pointer dereference a= t virtual address 0000000000000020 > [ 74.780130][ T2158] Mem abort info: > [ 74.780406][ T2158] ESR =3D 0x0000000096000004 > [ 74.780756][ T2158] EC =3D 0x25: DABT (current EL), IL =3D 32 bits > [ 74.781225][ T2158] SET =3D 0, FnV =3D 0 > [ 74.781529][ T2158] EA =3D 0, S1PTW =3D 0 > [ 74.781836][ T2158] FSC =3D 0x04: level 0 translation fault > [ 74.782288][ T2158] Data abort info: > [ 74.782577][ T2158] ISV =3D 0, ISS =3D 0x00000004, ISS2 =3D 0x000000= 00 > [ 74.783068][ T2158] CM =3D 0, WnR =3D 0, TnD =3D 0, TagAccess =3D 0 > [ 74.783533][ T2158] GCS =3D 0, Overlay =3D 0, DirtyBit =3D 0, Xs =3D= 0 > [ 74.784010][ T2158] user pgtable: 4k pages, 48-bit VAs, pgdp=3D0000000= 105f34000 > [ 74.784586][ T2158] [0000000000000020] pgd=3D0000000000000000, p4d=3D0= 000000000000000 > [ 74.785293][ T2158] Internal error: Oops: 0000000096000004 [#1] SMP > [ 74.785805][ T2158] Modules linked in: slub_kunit kunit ip6t_rpfilter = ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 xt_conntrack ebtable_n= at ebtable_broute ip6table_nat ip6table_mangle 4 > [ 74.790661][ T2158] CPU: 0 UID: 0 PID: 2158 Comm: kunit_try_catch Kdum= p: loaded Tainted: G W N 6.12.0-rc3+ #2 > [ 74.791535][ T2158] Tainted: [W]=3DWARN, [N]=3DTEST > [ 74.791889][ T2158] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.= 0 02/06/2015 > [ 74.792479][ T2158] pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -S= SBS BTYPE=3D--) > [ 74.793101][ T2158] pc : alloc_tagging_slab_alloc_hook+0x120/0x270 > [ 74.793607][ T2158] lr : alloc_tagging_slab_alloc_hook+0x120/0x270 > [ 74.794095][ T2158] sp : ffff800084d33cd0 > [ 74.794418][ T2158] x29: ffff800084d33cd0 x28: 0000000000000000 x27: 0= 000000000000000 > [ 74.795095][ T2158] x26: 0000000000000000 x25: 0000000000000012 x24: f= fff80007b30e314 > [ 74.795822][ T2158] x23: ffff000390ff6f10 x22: 0000000000000000 x21: 0= 000000000000088 > [ 74.796555][ T2158] x20: ffff000390285840 x19: fffffd7fc3ef7830 x18: f= fffffffffffffff > [ 74.797283][ T2158] x17: ffff8000800e63b4 x16: ffff80007b33afc4 x15: f= fff800081654c00 > [ 74.798011][ T2158] x14: 0000000000000000 x13: 205d383531325420 x12: 5= b5d383734363537 > [ 74.798744][ T2158] x11: ffff800084d337e0 x10: 000000000000005d x9 : 0= 0000000ffffffd0 > [ 74.799476][ T2158] x8 : 7f7f7f7f7f7f7f7f x7 : ffff80008219d188 x6 : c= 0000000ffff7fff > [ 74.800206][ T2158] x5 : ffff0003fdbc9208 x4 : ffff800081edd188 x3 : 0= 000000000000001 > [ 74.800932][ T2158] x2 : 0beaa6dee1ac5a00 x1 : 0beaa6dee1ac5a00 x0 : f= fff80037c2cb000 > [ 74.801656][ T2158] Call trace: > [ 74.801954][ T2158] alloc_tagging_slab_alloc_hook+0x120/0x270 > [ 74.802494][ T2158] __kmalloc_cache_noprof+0x148/0x33c > [ 74.802976][ T2158] test_kmalloc_redzone_access+0x4c/0x104 [slub_kuni= t] > [ 74.803607][ T2158] kunit_try_run_case+0x70/0x17c [kunit] > [ 74.804124][ T2158] kunit_generic_run_threadfn_adapter+0x2c/0x4c [kun= it] > [ 74.804768][ T2158] kthread+0x10c/0x118 > [ 74.805141][ T2158] ret_from_fork+0x10/0x20 > [ 74.805540][ T2158] Code: b9400a80 11000400 b9000a80 97ffd858 (f94012d= 3) > [ 74.806176][ T2158] SMP: stopping secondary CPUs > [ 74.808130][ T2158] Starting crashdump kernel... > > Fixes: e0a955bf7f61 ("mm/codetag: add pgalloc_tag_copy()") > Signed-off-by: Hao Ge > --- > v2: Modify the errors in the title and commit message. > Remove the empty lines that were mistakenly added in version v1. > --- > include/linux/alloc_tag.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h > index 1f0a9ff23a2c..8603e3a9df10 100644 > --- a/include/linux/alloc_tag.h > +++ b/include/linux/alloc_tag.h > @@ -137,10 +137,6 @@ static inline void alloc_tag_sub_check(union codetag= _ref *ref) {} > /* Caller should verify both ref and tag to be valid */ > static inline void __alloc_tag_ref_set(union codetag_ref *ref, struct al= loc_tag *tag) > { > - alloc_tag_add_check(ref, tag); > - if (!ref || !tag) > - return; > - Unfortunately this change will result in __alloc_tag_ref_set() and alloc_tag_ref_set() missing the following important check from alloc_tag_sub_check(): WARN_ONCE(ref && ref->ct, "alloc_tag was not cleared (got tag for %s:%u)\n", ref->ct->filename, ref->ct->lineno); I think the change below would fix this issue without the above mentioned side-effect: -static inline void __alloc_tag_ref_set(union codetag_ref *ref, struct alloc_tag *tag) +static inline bool __alloc_tag_ref_set(union codetag_ref *ref, struct alloc_tag *tag) { alloc_tag_add_check(ref, tag); if (!ref || !tag) - return; + return false; ref->ct =3D &tag->ct; + return true; } -static inline void alloc_tag_ref_set(union codetag_ref *ref, struct alloc_tag *tag) +static inline bool alloc_tag_ref_set(union codetag_ref *ref, struct alloc_tag *tag) { - __alloc_tag_ref_set(ref, tag); + if (unlikely(!__alloc_tag_ref_set(ref, tag))) + return false; + /* * We need in increment the call counter every time we have a new * allocation or when we split a large allocation into smaller ones= . * Each new reference for every sub-allocation needs to increment c= all * counter because when we free each part the counter will be decremented. */ this_cpu_inc(tag->counters->calls); + return true; } static inline void alloc_tag_add(union codetag_ref *ref, struct alloc_tag *tag, size_t bytes) { - alloc_tag_ref_set(ref, tag); - this_cpu_add(tag->counters->bytes, bytes); + if (likely(alloc_tag_ref_set(ref, tag))) + this_cpu_add(tag->counters->bytes, bytes); } Could you please confirm this fix? Thanks, Suren. > ref->ct =3D &tag->ct; > } > > @@ -158,6 +154,10 @@ static inline void alloc_tag_ref_set(union codetag_r= ef *ref, struct alloc_tag *t > > static inline void alloc_tag_add(union codetag_ref *ref, struct alloc_ta= g *tag, size_t bytes) > { > + alloc_tag_add_check(ref, tag); > + if (!ref || !tag) > + return; > + > alloc_tag_ref_set(ref, tag); > this_cpu_add(tag->counters->bytes, bytes); > } > -- > 2.25.1 >