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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1750069046; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=CJmMsPwVw446aTI6pY3bcI06UzOCZxFTiJIaMRiz8BM=; b=NqDAQrusYiozkJMjbecLgPWSpPUgVYzaYOKB10OO72Gk/BXkz7yDFP8Zej2nZgYw3rjjM6 tzgnP+PsCZH49AqtmskknjEvQOx+lADu1YLw8gzlsTJbn32qEszhQnAaS0rpduPRz/OkKa FkzGQT1LpTs2yBzz6nrA+Mz6wGMd2dk= X-MC-Unique: VyaUZZycOV6eZVGX28Jhaw-1 X-Mimecast-MFC-AGG-ID: VyaUZZycOV6eZVGX28Jhaw_1750069044 To: devel@lists.libvirt.org Subject: [PATCH] security_manager: Don't leak seclabel in virSecurityManagerGenLabel() Date: Mon, 16 Jun 2025 12:17:20 +0200 Message-ID: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: nrkbKm9f2pEqY_hbBAvEKFZYO5GgsYA40bFYq6pL9AQ_1750069044 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Message-ID-Hash: KAR3IEDNG25S5K5QC7MEZBUDTEDOBXCJ X-Message-ID-Hash: KAR3IEDNG25S5K5QC7MEZBUDTEDOBXCJ X-MailFrom: mprivozn@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-config-1; header-match-config-2; header-match-config-3; header-match-devel.lists.libvirt.org-0; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; suspicious-header X-Mailman-Version: 3.2.2 Precedence: list List-Id: Development discussions about the libvirt library & tools Archived-At: List-Archive: List-Help: List-Post: List-Subscribe: List-Unsubscribe: From: Michal Privoznik via Devel Reply-To: Michal Privoznik X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1750069070755116600 Content-Type: text/plain; charset="utf-8"; x-default="true" From: Michal Privoznik When a domain is being started, seclabels are generated for it. This is handled in virSecurityManagerGenLabel() which can either find pre-existing seclabel in domain def or generate a new one. At any rate, domainGenSecurityLabel() callback is called and if it fails then the seclabel is removed from domain definition using VIR_DELETE_ELEMENT(). While this shrinks down the seclabels array, it does not free individual item. It has to be freed manually. 80 bytes in 2 blocks are definitely lost in loss record 1,359 of 1,876 at 0x484CEF3: calloc (vg_replace_malloc.c:1675) by 0x4F19B29: g_malloc0 (in /usr/lib64/libglib-2.0.so.0.8200.5) by 0x49E4953: virSecurityLabelDefNew (virseclabel.c:59) by 0x4BDE0A4: virSecurityManagerGenLabel (security_manager.c:638) by 0xBA029B7: qemuProcessPrepareDomain (qemu_process.c:6760) by 0xBA07DF2: qemuProcessStart (qemu_process.c:8369) by 0xB93DAC0: qemuDomainObjStart (qemu_driver.c:6371) by 0xB93DE08: qemuDomainCreateWithFlags (qemu_driver.c:6420) by 0xB93DE86: qemuDomainCreate (qemu_driver.c:6438) by 0x4CECEA8: virDomainCreate (libvirt-domain.c:7142) Now, you might think this may lead to a double free, because @seclabel is freed under the 'cleanup' label (if @generated is true). But if @generated is true, then just before calling the callback there's VIR_APPEND_ELEMENT() which clears @seclabel out turning the free under 'cleanup' label into a NOP. Signed-off-by: Michal Privoznik Reviewed-by: J=C3=A1n Tomko --- src/security/security_manager.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/src/security/security_manager.c b/src/security/security_manage= r.c index c2460eae37..5fc4eb4872 100644 --- a/src/security/security_manager.c +++ b/src/security/security_manager.c @@ -669,9 +669,14 @@ virSecurityManagerGenLabel(virSecurityManager *mgr, VIR_APPEND_ELEMENT(vm->seclabels, vm->nseclabels, seclabel= ); =20 if (sec_managers[i]->drv->domainGenSecurityLabel(sec_managers[= i], vm) < 0) { + virSecurityLabelDef *tmp =3D vm->seclabels[vm->nseclabels = - 1]; + if (VIR_DELETE_ELEMENT(vm->seclabels, - vm->nseclabels -1, vm->nseclabels) = < 0) + vm->nseclabels - 1, vm->nseclabels)= < 0) { vm->nseclabels--; + } + + virSecurityLabelDefFree(tmp); goto cleanup; } =20 --=20 2.49.0