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charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261102-work-procfs-bugfixes-v1-24-59422ed3e465@kernel.org> References: <20261102-work-procfs-bugfixes-v1-0-59422ed3e465@kernel.org> In-Reply-To: <20261102-work-procfs-bugfixes-v1-0-59422ed3e465@kernel.org> 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 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=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9mJN9ymzS0mChk/OuHxLcK7hCIChOYcKK3y/vZOxX9 hTemFvv2lHKwiDGxSArpsji0G4SLrecp2KzUaYGzBxWJpAhDFycAjCRv4kM/3SchYRYG9b+Xrc8 wduJ9XImq3xMwSbxeTeYAicKTFfkvcLIcC/DZqdZ5/W1Oa+zPiduuy4Y56u/3qrMJ2nqgj3fHed 9YgUA X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 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