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Howlett" , Baoquan He , Pratyush Yadav , Pasha Tatashin , Jaroslav Kysela , Takashi Iwai , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Simona Vetter , Suren Baghdasaryan , Vlastimil Babka , Dave Young , linux-mm@kvack.org, linux-pci@vger.kernel.org, linux-sound@vger.kernel.org, kexec@lists.infradead.org, driver-core@lists.linux.dev Subject: [PATCH v2 3/3] proc: Unmap mmaps of removed files via file->f_mapping Date: Sat, 25 Jul 2026 21:05:49 +0000 Message-ID: <20260725210549.3716546-4-kwilczynski@kernel.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260725210549.3716546-1-kwilczynski@kernel.org> References: <20260725210549.3716546-1-kwilczynski@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A9547A0007 X-Stat-Signature: ph34o8jpabbwoydjyrqfy795cj9hsjhm X-HE-Tag: 1785013567-470438 X-HE-Meta: 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 ptN4zulo W2t9r1OIHyZ84IjbGiN9mOJ83h3vwlHN/AftkBc8dSx00U3USHGzqmIKgwLVq69o1jmpenz5zVNxu043DKJry/oogAjd27110/QBFQxTdGnMmuS8ueUU+RSkpuOFLvUuL8RpNldNxWVQ0oxcwviOAR57Y6LM3XUuE7wPygaDlqond6HSVS/xFgeIrMOvkqJUVZu0dtSaSKLQ6teXHnr7YrplF9gOwSd+NS9Ap16KkrOHMlGelIkYPFZNh1d54O3t//7UVWGD+Rnz9efDYf+36/rqmcaavUBR0u/TrPGo06UPI8MAMsoZwC4cWK3MhrLpuOQBgwaDWiwVUWDaBTAY7JrKoRg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Currently, proc_entry_rundown() releases every open file of an entry that is being removed, but never unmaps the userspace mappings created through those files, so these stay in place after the entry is gone. For the /proc/bus/pci device files, the VMAs of such mappings are attached to the shared iomem address space, as these files swap their f_mapping to iomem_get_mapping() at open time, see commit 636b21b50152 ("PCI: Revoke mappings like devmem"). As a result, userspace mappings of PCI BARs survive device removal, keeping stale PTEs into physical address space that the kernel may have reassigned since. Thus, use unmap_mapping_file() in close_pdeo() to unmap the pages of each open file, so that only the VMAs created through the removed file are zapped, while unrelated mappings on the shared address space are left intact. Add a pde_is_removed() helper next to pde_is_permanent() to tell a rundown from a regular close(), which leaves mappings alone, and use it in place of the open-coded checks in proc_misc_d_revalidate() and proc_misc_d_delete(). This reaches every removable entry with a proc_release() hook, not only the PCI ones. Other than /proc/bus/pci, the only entries that also set a proc_mmap() hook are /proc/vmcore and the ALSA information entries. Mappings of /proc/vmcore are now also unmapped when the entry is removed. The ALSA proc_mmap() hook calls a per-entry callback that no entry implements, so these cannot be mapped and nothing changes for them. A read through a stale mapping after removal now raises SIGBUS instead of returning stale data. Signed-off-by: Krzysztof Wilczyński --- fs/proc/generic.c | 4 ++-- fs/proc/inode.c | 2 ++ fs/proc/internal.h | 5 +++++ 3 files changed, 9 insertions(+), 2 deletions(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index adc9b9a092b0..0d090e3f3a26 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -222,14 +222,14 @@ static int proc_misc_d_revalidate(struct inode *dir, const struct qstr *name, if (flags & LOOKUP_RCU) return -ECHILD; - if (atomic_read(&PDE(d_inode(dentry))->in_use) < 0) + if (pde_is_removed(PDE(d_inode(dentry)))) return 0; /* revalidate */ return 1; } static int proc_misc_d_delete(const struct dentry *dentry) { - return atomic_read(&PDE(d_inode(dentry))->in_use) < 0; + return pde_is_removed(PDE(d_inode(dentry))); } static const struct dentry_operations proc_misc_dentry_ops = { diff --git a/fs/proc/inode.c b/fs/proc/inode.c index b7634f975d98..f1ebedc85b15 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -239,6 +239,8 @@ static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo) spin_unlock(&pde->pde_unload_lock); file = pdeo->file; + if (pde_is_removed(pde)) + unmap_mapping_file(file); pde->proc_ops->proc_release(file_inode(file), file); spin_lock(&pde->pde_unload_lock); diff --git a/fs/proc/internal.h b/fs/proc/internal.h index b232e1098117..53335381ae89 100644 --- a/fs/proc/internal.h +++ b/fs/proc/internal.h @@ -79,6 +79,11 @@ static inline bool pde_is_permanent(const struct proc_dir_entry *pde) return pde->flags & PROC_ENTRY_PERMANENT; } +static inline bool pde_is_removed(const struct proc_dir_entry *pde) +{ + return atomic_read(&pde->in_use) < 0; +} + /* This is for builtin code, not even for modules which are compiled in. */ static inline void pde_make_permanent(struct proc_dir_entry *pde) { -- 2.55.0