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fs/kernel_read_file: Switch buffer size arg to size_t

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In preparation for further refactoring of kernel_read_file*(), rename
the "max_size" argument to the more accurate "buf_size", and correct
its type to size_t. Add kerndoc to explain the specifics of how the
arguments will be used. Note that with buf_size now size_t, it can no
longer be negative (and was never called with a negative value). Adjust
callers to use it as a "maximum size" when *buf is NULL.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Acked-by: Scott Branden <scott.branden@broadcom.com>
Link: https://lore.kernel.org/r/20201002173828.2099543-7-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Kees Cook 2020-10-02 10:38:18 -07:00 committed by Greg Kroah-Hartman
parent f7a4f689bc
commit 113eeb5177
4 changed files with 31 additions and 15 deletions
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34
fs/kernel_read_file.c
View File

@ -5,15 +5,31 @@
#include <linux/security.h>
#include <linux/vmalloc.h>
/**
* kernel_read_file() - read file contents into a kernel buffer
*
* @file file to read from
* @buf pointer to a "void *" buffer for reading into (if
* *@buf is NULL, a buffer will be allocated, and
* @buf_size will be ignored)
* @buf_size size of buf, if already allocated. If @buf not
* allocated, this is the largest size to allocate.
* @id the kernel_read_file_id identifying the type of
* file contents being read (for LSMs to examine)
*
* Returns number of bytes read (no single read will be bigger
* than INT_MAX), or negative on error.
*
*/
int kernel_read_file(struct file *file, void **buf,
loff_t max_size, enum kernel_read_file_id id)
size_t buf_size, enum kernel_read_file_id id)
{
loff_t i_size, pos;
ssize_t bytes = 0;
void *allocated = NULL;
int ret;
if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
if (!S_ISREG(file_inode(file)->i_mode))
return -EINVAL;
ret = deny_write_access(file);
@ -29,7 +45,7 @@ int kernel_read_file(struct file *file, void **buf,
ret = -EINVAL;
goto out;
}
if (i_size > INT_MAX || (max_size > 0 && i_size > max_size)) {
if (i_size > INT_MAX || i_size > buf_size) {
ret = -EFBIG;
goto out;
}
@ -75,7 +91,7 @@ out:
EXPORT_SYMBOL_GPL(kernel_read_file);
int kernel_read_file_from_path(const char *path, void **buf,
loff_t max_size, enum kernel_read_file_id id)
size_t buf_size, enum kernel_read_file_id id)
{
struct file *file;
int ret;
@ -87,14 +103,14 @@ int kernel_read_file_from_path(const char *path, void **buf,
if (IS_ERR(file))
return PTR_ERR(file);
ret = kernel_read_file(file, buf, max_size, id);
ret = kernel_read_file(file, buf, buf_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 max_size,
size_t buf_size,
enum kernel_read_file_id id)
{
struct file *file;
@ -113,13 +129,13 @@ 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, max_size, id);
ret = kernel_read_file(file, buf, buf_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 max_size,
int kernel_read_file_from_fd(int fd, void **buf, size_t buf_size,
enum kernel_read_file_id id)
{
struct fd f = fdget(fd);
@ -128,7 +144,7 @@ int kernel_read_file_from_fd(int fd, void **buf, loff_t max_size,
if (!f.file)
goto out;
ret = kernel_read_file(f.file, buf, max_size, id);
ret = kernel_read_file(f.file, buf, buf_size, id);
out:
fdput(f);
return ret;

8
include/linux/kernel_read_file.h
View File

@ -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 max_size,
void **buf, size_t buf_size,
enum kernel_read_file_id id);
int kernel_read_file_from_path(const char *path,
void **buf, loff_t max_size,
void **buf, size_t buf_size,
enum kernel_read_file_id id);
int kernel_read_file_from_path_initns(const char *path,
void **buf, loff_t max_size,
void **buf, size_t buf_size,
enum kernel_read_file_id id);
int kernel_read_file_from_fd(int fd,
void **buf, loff_t max_size,
void **buf, size_t buf_size,
enum kernel_read_file_id id);
#endif /* _LINUX_KERNEL_READ_FILE_H */

2
security/integrity/digsig.c
View File

@ -175,7 +175,7 @@ int __init integrity_load_x509(const unsigned int id, const char *path)
int rc;
key_perm_t perm;
rc = kernel_read_file_from_path(path, &data, 0,
rc = kernel_read_file_from_path(path, &data, INT_MAX,
READING_X509_CERTIFICATE);
if (rc < 0) {
pr_err("Unable to open file: %s (%d)", path, rc);

2
security/integrity/ima/ima_fs.c
View File

@ -284,7 +284,7 @@ static ssize_t ima_read_policy(char *path)
datap = path;
strsep(&datap, "\n");
rc = kernel_read_file_from_path(path, &data, 0, READING_POLICY);
rc = kernel_read_file_from_path(path, &data, INT_MAX, READING_POLICY);
if (rc < 0) {
pr_err("Unable to open file: %s (%d)", path, rc);
return rc;