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b=kkCvPqeJt9hXEFyti3iJ1FwuLHxmLXyjHHLihOfXAuh24SOvF5m2sIXA2UBAh8zQQ tsZTpgZBpzYwBDlu66b4vShl+NYAJTi7OGk2wP7Ucha8AWhX9jcDy7R8S9N5GjeOby MOJMhwZqq5jk1LHpQtOrhu5TAJznkDJyCPku1XJuUlWnmjNp6Lg/pIqjCYjb2E9pRw PlIWcj69apuPJIahs9+j3NJIIhvqdlJy8k5li84RC/zXcbSfahqzG08MO06TAxTgGD MsdlO68zHBsAVPP5uOrOJ4ggSIX4Lm9icnN+egX0bDbSKuctAZGL1q6hKv1U57BXdn DGKynIt51Y7WQ== 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 RESEND v2 37/51] proc/vmcore: don't let vmcore_cleanup() run twice at once Date: Wed, 4 Nov 2026 20:25:02 +0100 Message-ID: <20261104-work-procfs-bugfixes-v2-37-021c84d852e0@kernel.org> In-Reply-To: <20261104-work-procfs-bugfixes-v2-0-021c84d852e0@kernel.org> References: <20261104-work-procfs-bugfixes-v2-0-021c84d852e0@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=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9bvzZL8Hl33wxMMfFJ8kjYsv9ztuaxT/NbubGcJp7u i+Umj2lo5SFQYyLQVZMkcWh3SRcbjlPxWajTA2YOaxMIEMYuDgFYCIcnxj+2TzZ/6BE4al+9D+l /+ZvBS6e1/KbqBD6LzUpOUjjyhHN2YwM69oa4jcaTUuZdOZNvK/7ramu9j/M3Cx9f4RUnOD8bDu LDQA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: 8bit X-Stat-Signature: f7gubdrsgqm3qj6kjfzpxbu7if4au9k1 X-Rspamd-Queue-Id: C38B9A0005 X-Rspam-User: X-Rspamd-Server: rspam08 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: 1793820317-29809 X-HE-Meta: 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 uV/12Yd3 ItjaKrvz9YzztMdahfz8xwheOym8+8NcKmVS6lH52BFchLneSl8yWqWL5NJlZ7YJAfTVx2kborsFiA4wSFyAZmdX6dqOw1as6XFDUhkvL8/RdodEToMLx7E4341I/f6v5vC2iLcf4QpH51ioEH+EZu/82AaPTqSb3gbJnDdajDGn/IP5pHBw9/jwB1BnrdqpVvfYzGZbmJq6+xAibJjwiyNliwy6NHllcRz/hyo25K7UXTiAa3qFwt22Y9S+3BmmDBNggSyiiXwz8tamth0jWxUtaivTComNISAygXfZMCESzyEsyoRaXYr2qPKxKx9u8iWPaZ95CIdSREMfIXvE3lb0cee1aiiLuZhCaJPqeD0P8oUyMjrBrUupvM4RnkGkTmV4aPo2cJ+0FFky47v1B/c5tpS3Lnye8oQDK7TQkbGMCN9HhytZBua7Jaiv6SX00p+cTXjWNqqkBRW0= 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