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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761323532; bh=QJbCv3dorbwltFD/bJzgSaTHfSbrFysNBhH68NyQCsQ=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=BQBvotmEc5dzMUOyFMp+OMBmfTgmrRhBErDoqsVtOUIac28Aei5feBsG+d6vWY+eH 4rAwrLMrav/Om5Wu+34l5Zh/ZdiKAZNe/spxILBg7OvBrf96+1l1WkxlPvIpTqvRQ7 o19C49hbbzpyKu3z4AaWqKMsgc3zYpt4hxwzt3IhoN+3GnU6ixD20eF3I/5RBJLXXV 6iLI27UaGc5v+ZFG/JA+jKVBH4F0mjV5CP/w8IDhuoCcMoM7xc6rvJ1jlUDafQxdnm nHkhw2WOVMOY7nsK5QmVCTsQspttcngQFPoqSJzd4afy/wK447GLF80f+oEiQqctyz ak5vAp0wzFTwQ== From: Pratyush Yadav To: Pasha Tatashin Cc: Pratyush Yadav , akpm@linux-foundation.org, brauner@kernel.org, corbet@lwn.net, graf@amazon.com, jgg@ziepe.ca, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, masahiroy@kernel.org, ojeda@kernel.org, rdunlap@infradead.org, rppt@kernel.org, tj@kernel.org Subject: Re: [PATCHv7 3/7] kho: drop notifiers In-Reply-To: (Pasha Tatashin's message of "Fri, 24 Oct 2025 12:15:32 -0400") References: <20251022005719.3670224-1-pasha.tatashin@soleen.com> <20251022005719.3670224-4-pasha.tatashin@soleen.com> Date: Fri, 24 Oct 2025 18:32:09 +0200 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 4703440005 X-Stat-Signature: cdkf68g4whmc855bwj4faexdxg3hwmxp X-HE-Tag: 1761323533-642614 X-HE-Meta: U2FsdGVkX192GjbdTFyShxR2hiatPIvTnjWaizVtBw0z7Y7JnMEar4bv4l+bHm3U+OCQ3wKYISqagrL2yK0bfBxCHfovK9KQONLTT7fyMNBaObbAOKdzeQYuuePRmA9fonsACrH3VMR/VYFWIyQs5V1f+kq3/eqkWj1eVAgh5hn6HJPZQGLUmhfc2F6vRj0k+xzdJVqB+t00mdYaLbrPy76onuMSckcI4MDcmiAVP1CzjjRAHDQNMsj64jhuMbrPe1C+zvUJwjZxt0YNho/qW4ZJwjq1HZQy4SDlx2/2ake0oNMrLaB04eTcNABYCRCKHr6u260IK5mLIdA0IVEl9l8grpKJUuvKBhO58280m0Hv9rxTnvEwPrJFAJ1G/Zzj5aa5fITc6rN7343nh27D0glrg5ul3iAWPpJcTH791tTjh2KEq6eG+pW/60cMDI/e/HZbESlcREeP+Cbrnu65aTXr7fWhCyyeRZ+lN4pnRSKEGsFErXvngwIvW/hTD/gFXVDf6f+KUPWTln3r95GXhBVtVUbpvpmjgS5mc2hPhVI3t+G5DdxopZlIkxvikSUvzSFBPEeGT9lKrbloyN/yOlAiiNqmpsNUWtdvwBYOrKCCPJy8cSreLvN0YWn0kUnKUiDQECTXtwdpGIE/sc3Zb5gOrcPuZhbyG+ArdAJ2+SY7OeNSBx+7rD9jMWmCXm/Z6yCQ0Dt+TZA87oSXHp0ujx30jQE+IfpalLX8e/90f+pJ98Xnm8r2afE2/AQZUS/ywXXhgXT5R1+sIhITOAL2Gytg1aczGuI+A/gMgGAAvfeZK4bcqn489sJl5nYHD2ZKipz2s/AYFO1VI/l0o43BUVCfbDGmm93ct/pREwgZ3pJfV3maCgKGWtoNY3VuKBW6jHCIlAHMhqqQmW/Y7ugmlCNAzxnpldCqlgdvbyOhHQkGAjHvRsWs4m5H8i1lXYOm64IMS9yx1hH/0Dxs9H5 dppd06my 7cXL4pcPm4dBdZq7KzCkpfTiV8jK0fQzXsDHYSdFrZ+dbEQQ89NAHYGVpfLeH47v5K1caoH2v0aeP2txWJCODo8NsfAgCib1jSb7rZpfcqUwUDVIwPYU0YhkRcr4fVPHj15igbzofJTZ8azTOpsC5LNB6Hmz0XjKeC0VqSmKMx03ySwYWL+5IIeCXyxyL3PJ+1TIcc73/4JDvvXA3x0BSW7CUZZwlBCxG24AKJID5QY8geKkMWTtH3fse0w== 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 Fri, Oct 24 2025, Pasha Tatashin wrote: > On Fri, Oct 24, 2025 at 11:52=E2=80=AFAM Pratyush Yadav wrote: >> >> On Fri, Oct 24 2025, Pratyush Yadav wrote: >> >> > On Fri, Oct 24 2025, Pasha Tatashin wrote: >> > >> >>> > -int kho_add_subtree(struct kho_serialization *ser, const char *na= me, void *fdt) >> >>> > +int kho_add_subtree(const char *name, void *fdt) >> >>> > { >> >>> > - int err =3D 0; >> >>> > - u64 phys =3D (u64)virt_to_phys(fdt); >> >>> > - void *root =3D page_to_virt(ser->fdt); >> >>> > + struct kho_sub_fdt *sub_fdt; >> >>> > + int err; >> >>> > >> >>> > - err |=3D fdt_begin_node(root, name); >> >>> > - err |=3D fdt_property(root, PROP_SUB_FDT, &phys, sizeof(phys= )); >> >>> > - err |=3D fdt_end_node(root); >> >>> > + sub_fdt =3D kmalloc(sizeof(*sub_fdt), GFP_KERNEL); >> >>> > + if (!sub_fdt) >> >>> > + return -ENOMEM; >> >>> > >> >>> > - if (err) >> >>> > - return err; >> >>> > + INIT_LIST_HEAD(&sub_fdt->l); >> >>> > + sub_fdt->name =3D name; >> >>> > + sub_fdt->fdt =3D fdt; >> >>> > >> >>> > - return kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false); >> >>> > + mutex_lock(&kho_out.fdts_lock); >> >>> > + list_add_tail(&sub_fdt->l, &kho_out.sub_fdts); >> >>> > + err =3D kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false); >> >>> >> >>> I think you should remove sub_fdt from the list and kfree() it on er= ror >> >>> here. Otherwise we signal an error to the caller and they might free >> >>> sub_fdt->fdt, which will later result in a use-after-free at >> >>> __kho_finalize(). >> >> >> >> I think, it is better to simply do: >> >> WARN_ON_ONCE(kho_debugfs_fdt_add(...)); >> >> Now debugfs is optional, and there is no reason to return an error to >> >> a caller if kho_debugfs_fdt_add() fails >> > >> > Yeah, that works too. >> >> On a second thought, maybe pr_warn() instead of WARN_ON()? This isn't an >> assertion since the debugfs creation can fail for many reasons. It isn't >> expected to always succeed. So a full WARN_ON() splat seems overkill. > > I sent it with WARN_ON_ONCE(), I can change it to pr_warn_once() if > there is another revision, otherwise we can just send a separate patch > to make the change it is not that important. Yep, makes sense. --=20 Regards, Pratyush Yadav