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Mon, 6 May 2024 15:41:33 +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 SV/vJS36OGblCgAAD6G6ig (envelope-from ); Mon, 06 May 2024 15:41:33 +0000 Date: Mon, 6 May 2024 17:41:28 +0200 From: Oscar Salvador To: Kees Cook Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Vlastimil Babka , Marco Elver , Andrey Konovalov , Alexander Potapenko , Alexandre Ghiti , syzbot+41bbfdb8d41003d12c0f@syzkaller.appspotmail.com Subject: Re: [PATCH v4 2/4] mm,page_owner: Fix refcount imbalance Message-ID: References: <20240404070702.2744-1-osalvador@suse.de> <20240404070702.2744-3-osalvador@suse.de> <202405060754.4405F8402F@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202405060754.4405F8402F@keescook> X-Rspam-User: X-Stat-Signature: ukn9s8qzyf9c51qkoyu83xuz8egywo7w X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: D8AD1160012 X-HE-Tag: 1715010095-32774 X-HE-Meta: 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 kbU1l8M0 gengEIc1tAEKVLdkbge2fKAv8ZXruNg1tk/tmUmJ8sjdKcV/vZ3G/c4EOhfq34tJOI8kR/mFOaE9ck5v/xE+gZnG4b8bGO1Xr61jx1o1jlNWlM0YTc6h5RD79gAC68RF5ZQF+g0WmnBQ5jkhJOWTmsCzOaltYSHWO+8j5WVNEU3Zwsio43JC1dXGAr0uaGhjeKP6cE+jVp38jfJ5HtpqZabMah9P2I9OIqmSPI05ERxg8o4+Bc4Hg2ICWIPaLgDthFXiQ6dcPJ2HxJdIWDi77eFRV/qNXl1pjStyaDMcs+1yT98xsxAzG3dsOdFl8Bw3X2c9/fprQwA3ar7QIMVQG0JWpQgNmpkMsQ+31byV2rF/fcumSZhymrnJkumRDPEK0fC/1lPcDdbjNHdA4l9W1pUO+BV9+q66Q+LXexkPyVKId601bdZWnEg9XwA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 Mon, May 06, 2024 at 07:59:11AM -0700, Kees Cook wrote: > Does this also fix this? > https://lore.kernel.org/all/202405061514.23fedba1-oliver.sang@intel.com/ Hi Kess, yes, it does. > > This is a report of the backtrace changing, but the warning was > pre-existing. > > > [...] > > -static void dec_stack_record_count(depot_stack_handle_t handle) > > +static void dec_stack_record_count(depot_stack_handle_t handle, > > + int nr_base_pages) > > { > > struct stack_record *stack_record = __stack_depot_get_stack_record(handle); > > > > - if (stack_record) > > - refcount_dec(&stack_record->count); > > + if (!stack_record) > > + return; > > + > > + if (refcount_sub_and_test(nr_base_pages, &stack_record->count)) > > + pr_warn("%s: refcount went to 0 for %u handle\n", __func__, > > + handle); > > This pr_warn() isn't needed: refcount will very loudly say the same > thing. :) Yes, but I wanted to get the handle so I can match it with the backtrace. Thanks -- Oscar Salvador SUSE Labs