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b=WdWrZpQZG3jkjCCQpsfQrBfgI1HDfynUYNY6vSK8rFGYC+yFDlqVfIlEyf4lUkT0P 47Qva0HSuMAdzfViLwsaTOh+Gv11NHerf7rOfu6InrqZM/g/ogcoP2D8FesuH1O8lI hy7orIASJbsGEcOppEShVEs3qXLaqbCm2X1l58C/mLO7S3SSho647wFT/6dMID+10o OEsRp/bw90rGUnntzwTIKbrSuRSgPWrqC9DAx8itOX9VTQCmMsQmbO+kpoEevaaznU jpanOJfr9ANyVI0+/ZlgBo3nJ2sRa69PFXETlEYKduVxU+xF7MZ1giUdKYjN5C4/6X bQ/q4gyj9YA2A== From: Christian Brauner To: linux-fsdevel@vger.kernel.org Cc: Linus Torvalds , Jann Horn , Josef Bacik , Chris Mason , Jeff Layton , NeilBrown , Eric Dumazet , Thomas Gleixner , Al Viro , Jonathan Corbet , Christoph Hellwig , Greg Kroah-Hartman , Joel Granados , Kees Cook , Jan Kara , Jan Kara , linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-um@lists.infradead.org, linux-wireless@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, ntfs3@lists.linux.dev, platform-driver-x86@vger.kernel.org, coreteam@netfilter.org, kexec@lists.infradead.org, linux-pci@vger.kernel.org, linux-sound@vger.kernel.org, netfilter-devel@vger.kernel.org, dri-devel@lists.freedesktop.org, ibm-acpi-devel@lists.sourceforge.net, jfs-discussion@lists.sourceforge.net, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-cifs@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-mm@kvack.org, linux-sh@vger.kernel.org, linux-usb@vger.kernel.org, samba-technical@lists.samba.org, sparclinux@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-doc@vger.kernel.org, linux-serial@vger.kernel.org, linux-atm-general@lists.sourceforge.net, Takashi Iwai , linux-input@vger.kernel.org, linux-raid@vger.kernel.org, linux-ext4@vger.kernel.org, linux-modules@vger.kernel.org, linux-debuggers@vger.kernel.org, "Christian Brauner (Amutable)" , Chuck Lever , stable@vger.kernel.org Subject: [PATCH v2 37/51] proc/vmcore: don't let vmcore_cleanup() run twice at once Date: Wed, 4 Nov 2026 18:47:23 +0100 Message-ID: <20261104-work-procfs-bugfixes-v2-37-bbf7d5546809@kernel.org> In-Reply-To: <20261104-work-procfs-bugfixes-v2-0-bbf7d5546809@kernel.org> References: <20261104-work-procfs-bugfixes-v2-0-bbf7d5546809@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=1758; i=brauner@kernel.org; h=from:subject:message-id; bh=gmON/Vwu30bm66aR7FLjt15bWl4pslPspuVjwp92LoI=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9zntzeuekQwxr7P0OOe39UCH++f+GeYsr8k/NVg0Tb VTs/Xvpc0cpC4MYF4OsmCKLQ7tJuNxynorNRpkaMHNYmUCGMHBxCsBEwtsZGWZcnzuvlVNJw+uO fOP1dOFrwRJ3O9wSfjxvbSqZ8obd7yEjw9/p+SJB0Us0z7YI1mVedF7t1tNceCBK08xCfvPP1Pt LeAA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: D3A74A0007 X-Stat-Signature: xuabgiidj5thjx5u5jrenpmf6rk367q6 X-Rspam-User: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-HE-Tag: 1793814983-755019 X-HE-Meta: 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 v5llhHNg sc2TYTavLI8bH+rdXSy/aeFiIJVbIBLUt1x61r706ZavMb5Esm1wKYDbIyW1KWpcKEuPy43dfcKWoL3Q+Qrb4BWC2VSMYBsCbM5fKlx341bBsqgN5gRJS/3Ji2YDOxj298w6gN7yFO1si6L+V2Sdu8lfaNw26NFCp8dMSiL/QIqezPPGUAB3xAREjJLfGoOVW/8f0L+5pzjYLDIWnahLByndjJQtpCWfp2ABhiebKJQ5rEgSRvdpbsYc/qArH5z5+yC/3siA1TBtrkbqn3k8LH/XsGJCOpz6PYbMwpRBa9sFDBVBEmsPB6csJV/ZqD0//tn2wRTYvS9+eADrZpaAIEAcElL0qL9qBAPpXxEAplzxCUTx3eDdn8Z4EJdNyhxiRbwzqQdHRKiNmA8BsvokjT4Td0DpclpOh80WhboE0SZHhQYDt12A9mrwe7n3u6o/EvS89 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 vmcore_cleanup() has a single caller, fadump's release_mem_store() on powerpc. That checks fw_dump.dump_active without a lock and calls vmcore_cleanup() without one, and kernfs only serializes the writers of one open file. So two tasks that write to /sys/kernel/fadump/release_mem through different files run vmcore_cleanup() at the same time. The first one removes /proc/vmcore and waits for its readers in proc_remove(). The second one finds the entry already unlinked, returns from proc_remove() right away and frees vmcore_list, the ELF headers and the device dumps while those readers still walk them. Or both of them free the same lists at once. Serialize vmcore_cleanup() with a mutex of its own. It can't be vmcore_mutex, removing /proc/vmcore calls release_vmcore() which takes it. The second caller then finds nothing left to free. Reported-by: Chris Mason Fixes: b500afff11f6 ("fadump: Invalidate registration and release reserved memory for general use.") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner (Amutable) --- fs/proc/vmcore.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c index 1fe70c4ecc54..ccb795b85509 100644 --- a/fs/proc/vmcore.c +++ b/fs/proc/vmcore.c @@ -1764,6 +1764,11 @@ fs_initcall(vmcore_init); /* Cleanup function for vmcore module. */ void vmcore_cleanup(void) { + /* Not vmcore_mutex, removing /proc/vmcore calls release_vmcore(). */ + static DEFINE_MUTEX(vmcore_cleanup_mutex); + + /* Two writers of fadump's release_mem can get here at once. */ + guard(mutex)(&vmcore_cleanup_mutex); if (proc_vmcore) { proc_remove(proc_vmcore); proc_vmcore = NULL; -- 2.53.0