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Message-ID: <ad1f7aa8-0b20-b611-d35f-5cdba33e0b7e@broadcom.com>
Date: Fri, 17 Jul 2020 12:55:37 -0700
From: Scott Branden <scott.branden@...adcom.com>
To: Kees Cook <keescook@...omium.org>
Cc: Mimi Zohar <zohar@...ux.ibm.com>,
Matthew Wilcox <willy@...radead.org>,
James Morris <jmorris@...ei.org>,
Luis Chamberlain <mcgrof@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Jessica Yu <jeyu@...nel.org>,
Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
"Serge E. Hallyn" <serge@...lyn.com>,
Casey Schaufler <casey@...aufler-ca.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Peter Zijlstra <peterz@...radead.org>,
Matthew Garrett <matthewgarrett@...gle.com>,
David Howells <dhowells@...hat.com>,
Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
Randy Dunlap <rdunlap@...radead.org>,
"Joel Fernandes (Google)" <joel@...lfernandes.org>,
KP Singh <kpsingh@...gle.com>, Dave Olsthoorn <dave@...aar.me>,
Hans de Goede <hdegoede@...hat.com>,
Peter Jones <pjones@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Stephen Boyd <stephen.boyd@...aro.org>,
Paul Moore <paul@...l-moore.com>,
Stephen Smalley <stephen.smalley.work@...il.com>,
linux-security-module@...r.kernel.org,
linux-integrity@...r.kernel.org, selinux@...r.kernel.org,
linux-fsdevel@...r.kernel.org, kexec@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/13] fs/kernel_read_file: Remove redundant size argument
On 2020-07-17 12:04 p.m., Scott Branden wrote:
> Hi Kees,
>
> On 2020-07-17 10:43 a.m., Kees Cook wrote:
>> In preparation for refactoring kernel_read_file*(), remove the redundant
>> "size" argument which is not needed: it can be included in the return
> I don't think the size argument is redundant though.
> The existing kernel_read_file functions always read the whole file.
> Now, what happens if the file is bigger than the buffer.
> How does kernel_read_file know it read the whole file by looking at
> the return value?
Actually, this change looks ok dealing with the size. I'll look at the
rest.
>
>> code, with callers adjusted. (VFS reads already cannot be larger than
>> INT_MAX.)
>>
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>> ---
>> drivers/base/firmware_loader/main.c | 8 ++++----
>> fs/kernel_read_file.c | 20 +++++++++-----------
>> include/linux/kernel_read_file.h | 8 ++++----
>> kernel/kexec_file.c | 13 ++++++-------
>> kernel/module.c | 7 +++----
>> security/integrity/digsig.c | 5 +++--
>> security/integrity/ima/ima_fs.c | 5 +++--
>> 7 files changed, 32 insertions(+), 34 deletions(-)
>>
>> diff --git a/drivers/base/firmware_loader/main.c
>> b/drivers/base/firmware_loader/main.c
>> index d4a413ea48ce..ea419c7d3d34 100644
>> --- a/drivers/base/firmware_loader/main.c
>> +++ b/drivers/base/firmware_loader/main.c
>> @@ -462,7 +462,7 @@ fw_get_filesystem_firmware(struct device *device,
>> struct fw_priv *fw_priv,
>> size_t in_size,
>> const void *in_buffer))
>> {
>> - loff_t size;
>> + size_t size;
>> int i, len;
>> int rc = -ENOENT;
>> char *path;
>> @@ -494,10 +494,9 @@ fw_get_filesystem_firmware(struct device
>> *device, struct fw_priv *fw_priv,
>> fw_priv->size = 0;
>> /* load firmware files from the mount namespace of init */
>> - rc = kernel_read_file_from_path_initns(path, &buffer,
>> - &size, msize,
>> + rc = kernel_read_file_from_path_initns(path, &buffer, msize,
>> READING_FIRMWARE);
>> - if (rc) {
>> + if (rc < 0) {
>> if (rc != -ENOENT)
>> dev_warn(device, "loading %s failed with error %d\n",
>> path, rc);
>> @@ -506,6 +505,7 @@ fw_get_filesystem_firmware(struct device *device,
>> struct fw_priv *fw_priv,
>> path);
>> continue;
>> }
>> + size = rc;
>> dev_dbg(device, "Loading firmware from %s\n", path);
>> if (decompress) {
>> dev_dbg(device, "f/w decompressing %s\n",
>> diff --git a/fs/kernel_read_file.c b/fs/kernel_read_file.c
>> index 54d972d4befc..dc28a8def597 100644
>> --- a/fs/kernel_read_file.c
>> +++ b/fs/kernel_read_file.c
>> @@ -5,7 +5,7 @@
>> #include <linux/security.h>
>> #include <linux/vmalloc.h>
>> -int kernel_read_file(struct file *file, void **buf, loff_t *size,
>> +int kernel_read_file(struct file *file, void **buf,
>> loff_t max_size, enum kernel_read_file_id id)
>> {
>> loff_t i_size, pos;
>> @@ -29,7 +29,7 @@ int kernel_read_file(struct file *file, void **buf,
>> loff_t *size,
>> ret = -EINVAL;
>> goto out;
>> }
>> - if (i_size > SIZE_MAX || (max_size > 0 && i_size > max_size)) {
>> + if (i_size > INT_MAX || (max_size > 0 && i_size > max_size)) {
> Should this be SSIZE_MAX?
>> ret = -EFBIG;
>> goto out;
>> }
>> @@ -59,8 +59,6 @@ int kernel_read_file(struct file *file, void **buf,
>> loff_t *size,
>> }
>> ret = security_kernel_post_read_file(file, *buf, i_size, id);
>> - if (!ret)
>> - *size = pos;
>> out_free:
>> if (ret < 0) {
>> @@ -72,11 +70,11 @@ int kernel_read_file(struct file *file, void
>> **buf, loff_t *size,
>> out:
>> allow_write_access(file);
>> - return ret;
>> + return ret == 0 ? pos : ret;
>> }
>> EXPORT_SYMBOL_GPL(kernel_read_file);
>> -int kernel_read_file_from_path(const char *path, void **buf,
>> loff_t *size,
>> +int kernel_read_file_from_path(const char *path, void **buf,
>> loff_t max_size, enum kernel_read_file_id id)
>> {
>> struct file *file;
>> @@ -89,14 +87,14 @@ int kernel_read_file_from_path(const char *path,
>> void **buf, loff_t *size,
>> if (IS_ERR(file))
>> return PTR_ERR(file);
>> - ret = kernel_read_file(file, buf, size, max_size, id);
>> + ret = kernel_read_file(file, buf, max_size, id);
>> fput(file);
>> return ret;
>> }
>> EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
>> int kernel_read_file_from_path_initns(const char *path, void **buf,
>> - loff_t *size, loff_t max_size,
>> + loff_t max_size,
>> enum kernel_read_file_id id)
>> {
>> struct file *file;
>> @@ -115,13 +113,13 @@ int kernel_read_file_from_path_initns(const
>> char *path, void **buf,
>> if (IS_ERR(file))
>> return PTR_ERR(file);
>> - ret = kernel_read_file(file, buf, size, max_size, id);
>> + ret = kernel_read_file(file, buf, max_size, id);
>> fput(file);
>> return ret;
>> }
>> EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns);
>> -int kernel_read_file_from_fd(int fd, void **buf, loff_t *size,
>> loff_t max_size,
>> +int kernel_read_file_from_fd(int fd, void **buf, loff_t max_size,
>> enum kernel_read_file_id id)
>> {
>> struct fd f = fdget(fd);
>> @@ -130,7 +128,7 @@ int kernel_read_file_from_fd(int fd, void **buf,
>> loff_t *size, loff_t max_size,
>> if (!f.file)
>> goto out;
>> - ret = kernel_read_file(f.file, buf, size, max_size, id);
>> + ret = kernel_read_file(f.file, buf, max_size, id);
>> out:
>> fdput(f);
>> return ret;
>> diff --git a/include/linux/kernel_read_file.h
>> b/include/linux/kernel_read_file.h
>> index 78cf3d7dc835..0ca0bdbed1bd 100644
>> --- a/include/linux/kernel_read_file.h
>> +++ b/include/linux/kernel_read_file.h
>> @@ -36,16 +36,16 @@ static inline const char
>> *kernel_read_file_id_str(enum kernel_read_file_id id)
>> }
>> int kernel_read_file(struct file *file,
>> - void **buf, loff_t *size, loff_t max_size,
>> + void **buf, loff_t max_size,
>> enum kernel_read_file_id id);
>> int kernel_read_file_from_path(const char *path,
>> - void **buf, loff_t *size, loff_t max_size,
>> + void **buf, loff_t max_size,
>> enum kernel_read_file_id id);
>> int kernel_read_file_from_path_initns(const char *path,
>> - void **buf, loff_t *size, loff_t max_size,
>> + void **buf, loff_t max_size,
>> enum kernel_read_file_id id);
>> int kernel_read_file_from_fd(int fd,
>> - void **buf, loff_t *size, loff_t max_size,
>> + void **buf, loff_t max_size,
>> enum kernel_read_file_id id);
>> #endif /* _LINUX_KERNEL_READ_FILE_H */
>> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
>> index 1358069ce9e9..a201bbb19158 100644
>> --- a/kernel/kexec_file.c
>> +++ b/kernel/kexec_file.c
>> @@ -220,13 +220,12 @@ kimage_file_prepare_segments(struct kimage
>> *image, int kernel_fd, int initrd_fd,
>> {
>> int ret;
>> void *ldata;
>> - loff_t size;
>> ret = kernel_read_file_from_fd(kernel_fd, &image->kernel_buf,
>> - &size, INT_MAX, READING_KEXEC_IMAGE);
>> - if (ret)
>> + INT_MAX, READING_KEXEC_IMAGE);
>> + if (ret < 0)
>> return ret;
>> - image->kernel_buf_len = size;
>> + image->kernel_buf_len = ret;
>> /* Call arch image probe handlers */
>> ret = arch_kexec_kernel_image_probe(image, image->kernel_buf,
>> @@ -243,11 +242,11 @@ kimage_file_prepare_segments(struct kimage
>> *image, int kernel_fd, int initrd_fd,
>> /* It is possible that there no initramfs is being loaded */
>> if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
>> ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf,
>> - &size, INT_MAX,
>> + INT_MAX,
>> READING_KEXEC_INITRAMFS);
>> - if (ret)
>> + if (ret < 0)
>> goto out;
>> - image->initrd_buf_len = size;
>> + image->initrd_buf_len = ret;
>> }
>> if (cmdline_len) {
>> diff --git a/kernel/module.c b/kernel/module.c
>> index e9765803601b..b6fd4f51cc30 100644
>> --- a/kernel/module.c
>> +++ b/kernel/module.c
>> @@ -3988,7 +3988,6 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
>> SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs,
>> int, flags)
>> {
>> struct load_info info = { };
>> - loff_t size;
>> void *hdr = NULL;
>> int err;
>> @@ -4002,12 +4001,12 @@ SYSCALL_DEFINE3(finit_module, int, fd,
>> const char __user *, uargs, int, flags)
>> |MODULE_INIT_IGNORE_VERMAGIC))
>> return -EINVAL;
>> - err = kernel_read_file_from_fd(fd, &hdr, &size, INT_MAX,
>> + err = kernel_read_file_from_fd(fd, &hdr, INT_MAX,
>> READING_MODULE);
>> - if (err)
>> + if (err < 0)
>> return err;
>> info.hdr = hdr;
>> - info.len = size;
>> + info.len = err;
>> return load_module(&info, uargs, flags);
>> }
>> diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
>> index f8869be45d8f..97661ffabc4e 100644
>> --- a/security/integrity/digsig.c
>> +++ b/security/integrity/digsig.c
>> @@ -171,16 +171,17 @@ int __init integrity_add_key(const unsigned int
>> id, const void *data,
>> int __init integrity_load_x509(const unsigned int id, const char
>> *path)
>> {
>> void *data = NULL;
>> - loff_t size;
>> + size_t size;
>> int rc;
>> key_perm_t perm;
>> - rc = kernel_read_file_from_path(path, &data, &size, 0,
>> + rc = kernel_read_file_from_path(path, &data, 0,
>> READING_X509_CERTIFICATE);
>> if (rc < 0) {
>> pr_err("Unable to open file: %s (%d)", path, rc);
>> return rc;
>> }
>> + size = rc;
>> perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW |
>> KEY_USR_READ;
>> diff --git a/security/integrity/ima/ima_fs.c
>> b/security/integrity/ima/ima_fs.c
>> index e13ffece3726..9ba145d3d6d9 100644
>> --- a/security/integrity/ima/ima_fs.c
>> +++ b/security/integrity/ima/ima_fs.c
>> @@ -275,7 +275,7 @@ static ssize_t ima_read_policy(char *path)
>> {
>> void *data = NULL;
>> char *datap;
>> - loff_t size;
>> + size_t size;
>> int rc, pathlen = strlen(path);
>> char *p;
>> @@ -284,11 +284,12 @@ static ssize_t ima_read_policy(char *path)
>> datap = path;
>> strsep(&datap, "\n");
>> - rc = kernel_read_file_from_path(path, &data, &size, 0,
>> READING_POLICY);
>> + rc = kernel_read_file_from_path(path, &data, 0, READING_POLICY);
>> if (rc < 0) {
>> pr_err("Unable to open file: %s (%d)", path, rc);
>> return rc;
>> }
>> + size = rc;
>> datap = data;
>> while (size > 0 && (p = strsep(&datap, "\n"))) {
>
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