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Fri, 26 Sep 2025 12:48:14 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 5eFoDI6L1mhjSwAAD6G6ig (envelope-from ); Fri, 26 Sep 2025 12:48:14 +0000 Message-ID: <96d00a94-1a4b-4378-8d89-0554f89778e1@suse.cz> Date: Fri, 26 Sep 2025 14:48:13 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH linux-next] alloc_tag: Fix boot failure due to NULL pointer dereference Content-Language: en-US To: ranxiaokai627@163.com, akpm@linux-foundation.org, cl@gentwo.org, rientjes@google.com, roman.gushchin@linux.dev, harry.yoo@oracle.com, usamaarif642@gmail.com, surenb@google.com, shakeel.butt@linux.dev, hannes@cmpxchg.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, ran.xiaokai@zte.com.cn References: <20250926080659.741991-1-ranxiaokai627@163.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Level: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.999]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_TO(0.00)[163.com,linux-foundation.org,gentwo.org,google.com,linux.dev,oracle.com,gmail.com,cmpxchg.org]; MID_RHS_MATCH_FROM(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_ENVRCPT(0.00)[163.com,gmail.com]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_TWELVE(0.00)[13]; RCVD_TLS_ALL(0.00)[]; TO_DN_NONE(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.cz:email,suse.cz:mid] X-Spam-Flag: NO X-Spam-Score: -4.30 On 9/26/25 10:06, ranxiaokai627@163.com wrote: > From: Ran Xiaokai > > There is a boot failure when both CONFIG_DEBUG_KMEMLEAK and > CONFIG_MEM_ALLOC_PROFILING are enabled. > > BUG: kernel NULL pointer dereference, address: 0000000000000000 > RIP: 0010:__alloc_tagging_slab_alloc_hook+0x181/0x2f0 > Call Trace: > kmem_cache_alloc_noprof+0x1c8/0x5c0 > __alloc_object+0x2f/0x290 > __create_object+0x22/0x80 > kmemleak_init+0x122/0x190 > mm_core_init+0xb6/0x160 > start_kernel+0x39f/0x920 > x86_64_start_reservations+0x18/0x30 > x86_64_start_kernel+0x104/0x120 > common_startup_64+0x12c/0x138 > > In kmemleak, mem_pool_alloc() directly calls kmem_cache_alloc_noprof(), > as a result, the alloc_tag structure associated with object_cache is not > defined neither initialized. So current->alloc_tag is NULL, > leading to a null pointer dereference. Agree with Harry. This should be enough: "as a result, current->alloc_tag is NULL, leading to a null pointer dereference." > Move the checks for SLAB_NO_OBJ_EXT, SLAB_NOLEAKTRACE, and > __GFP_NO_OBJ_EXT to the parent function __alloc_tagging_slab_alloc_hook() > to fix this. > > Also this distinguishes the SLAB_NOLEAKTRACE case between the actual memory > allocation failures case, make CODETAG_FLAG_INACCURATE more accurate. Good point. > Fixes: b9e2f58ffb84 ("alloc_tag: mark inaccurate allocation counters in /proc/allocinfo output") That's in mm-stable so the fix should go there (probably too late to fold now) if it's to be in the merge window PR. > Signed-off-by: Ran Xiaokai Acked-by: Vlastimil Babka > --- > mm/slub.c | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 867a07260acf..09cbe580842c 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -2197,15 +2197,6 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p) > { > struct slab *slab; > > - if (!p) > - return NULL; > - > - if (s->flags & (SLAB_NO_OBJ_EXT | SLAB_NOLEAKTRACE)) > - return NULL; > - > - if (flags & __GFP_NO_OBJ_EXT) > - return NULL; > - > slab = virt_to_slab(p); > if (!slab_obj_exts(slab) && > alloc_slab_obj_exts(slab, s, flags, false)) { > @@ -2223,6 +2214,15 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags) > { > struct slabobj_ext *obj_exts; > > + if (!object) > + return; > + > + if (s->flags & (SLAB_NO_OBJ_EXT | SLAB_NOLEAKTRACE)) > + return; > + > + if (flags & __GFP_NO_OBJ_EXT) > + return; > + > obj_exts = prepare_slab_obj_exts_hook(s, flags, object); > /* > * Currently obj_exts is used only for allocation profiling.