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Wysocki" , Len Brown , linux-kernel@vger.kernel.org, rui.zhang@intel.com, Pedro Falcato , Hang Zhang , Swift Geek Subject: [PATCH] ACPI: Make custom_method use per-open state Date: Tue, 31 Jan 2023 23:37:55 +0000 Message-Id: <20230131233755.58942-1-pedro.falcato@gmail.com> X-Mailer: git-send-email 2.39.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Make custom_method keep its own per-file-open state instead of global state in order to avoid race conditions[1] and other possible conflicts with other concurrent users. Link: https://lore.kernel.org/linux-acpi/20221227063335.61474-1-zh.nvgt@gmail.com/ # [1] Reported-by: Hang Zhang Cc: Swift Geek Signed-off-by: Pedro Falcato --- This patch addresses Hang's problems plus the ones raised by Rafael in his review (see link above). https://lore.kernel.org/lkml/2667007.mvXUDI8C0e@kreacher/ was submitted but since there were still people that wanted this feature, I took my time to write up a patch that should fix the issues. Hopefully the linux-acpi maintainers have not decided to remove custom_method just yet. drivers/acpi/custom_method.c | 119 +++++++++++++++++++++++++++-------- 1 file changed, 92 insertions(+), 27 deletions(-) diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c index d39a9b47472..034fb14f118 100644 --- a/drivers/acpi/custom_method.c +++ b/drivers/acpi/custom_method.c @@ -17,73 +17,138 @@ MODULE_LICENSE("GPL"); static struct dentry *cm_dentry; +struct custom_method_state { + char *buf; + u32 max_size; + u32 uncopied_bytes; + struct mutex lock; +}; + +static int cm_open(struct inode *inode, struct file *file) +{ + struct custom_method_state *state; + + state = kzalloc(sizeof(struct custom_method_state), GFP_KERNEL); + + if (!state) + return -ENOMEM; + + file->private_data = state; + mutex_init(&state->lock); + + return 0; +} + +static int cm_release(struct inode *inode, struct file *file) +{ + struct custom_method_state *state; + + state = file->private_data; + + mutex_destroy(&state->lock); + + /* Make sure the buf gets freed */ + kfree(state->buf); + + kfree(state); + return 0; +} + /* /sys/kernel/debug/acpi/custom_method */ static ssize_t cm_write(struct file *file, const char __user *user_buf, size_t count, loff_t *ppos) { - static char *buf; - static u32 max_size; - static u32 uncopied_bytes; + struct custom_method_state *state; + char *buf; struct acpi_table_header table; acpi_status status; int ret; + state = file->private_data; + buf = state->buf; + ret = security_locked_down(LOCKDOWN_ACPI_TABLES); if (ret) return ret; + mutex_lock(&state->lock); + if (!(*ppos)) { /* parse the table header to get the table length */ - if (count <= sizeof(struct acpi_table_header)) - return -EINVAL; + if (count <= sizeof(struct acpi_table_header)) { + count = -EINVAL; + goto out; + } + if (copy_from_user(&table, user_buf, - sizeof(struct acpi_table_header))) - return -EFAULT; - uncopied_bytes = max_size = table.length; + sizeof(struct acpi_table_header))) { + count = -EFAULT; + goto out; + } + + state->uncopied_bytes = state->max_size = table.length; /* make sure the buf is not allocated */ kfree(buf); - buf = kzalloc(max_size, GFP_KERNEL); - if (!buf) - return -ENOMEM; + buf = state->buf = kzalloc(state->max_size, GFP_KERNEL); + if (!buf) { + count = -ENOMEM; + goto out; + } } - if (buf == NULL) - return -EINVAL; + /* Check if someone seeked ahead or if we errored out + * (buf will be NULL) + */ + if (buf == NULL) { + count = -EINVAL; + goto out; + } - if ((*ppos > max_size) || - (*ppos + count > max_size) || + if ((*ppos > state->max_size) || + (*ppos + count > state->max_size) || (*ppos + count < count) || - (count > uncopied_bytes)) { - kfree(buf); - buf = NULL; - return -EINVAL; + (count > state->uncopied_bytes)) { + count = -EINVAL; + goto err_free; } if (copy_from_user(buf + (*ppos), user_buf, count)) { - kfree(buf); - buf = NULL; - return -EFAULT; + count = -EFAULT; + goto err_free; } - uncopied_bytes -= count; + state->uncopied_bytes -= count; *ppos += count; - if (!uncopied_bytes) { + if (!state->uncopied_bytes) { status = acpi_install_method(buf); kfree(buf); - buf = NULL; - if (ACPI_FAILURE(status)) - return -EINVAL; + state->buf = NULL; + + if (ACPI_FAILURE(status)) { + count = -EINVAL; + goto out; + } + add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE); } +out: + mutex_unlock(&state->lock); + return count; +err_free: + mutex_unlock(&state->lock); + kfree(buf); + state->buf = NULL; return count; } static const struct file_operations cm_fops = { .write = cm_write, + .open = cm_open, + .release = cm_release, .llseek = default_llseek, }; -- 2.39.0