Relax the rw_verify_area() error checking.
In particular, allow over-large read- or write-requests to be downgraded
to a more reasonable range, rather than considering them outright errors.
We want to protect lower layers from (the sadly all too common) overflow
conditions, but prefer to do so by chopping the requests up, rather than
just refusing them outright.
Cc: Peter Anvin <hpa@zytor.com>
Cc: Ulrich Drepper <drepper@redhat.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Al Viro <viro@ftp.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/read_write.c b/fs/read_write.c
index a091ee4..df3468a 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -14,6 +14,7 @@
#include <linux/security.h>
#include <linux/module.h>
#include <linux/syscalls.h>
+#include <linux/pagemap.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
@@ -182,22 +183,33 @@
}
#endif
+/*
+ * rw_verify_area doesn't like huge counts. We limit
+ * them to something that fits in "int" so that others
+ * won't have to do range checks all the time.
+ */
+#define MAX_RW_COUNT (INT_MAX & PAGE_CACHE_MASK)
int rw_verify_area(int read_write, struct file *file, loff_t *ppos, size_t count)
{
struct inode *inode;
loff_t pos;
- if (unlikely(count > INT_MAX))
+ if (unlikely((ssize_t) count < 0))
goto Einval;
pos = *ppos;
if (unlikely((pos < 0) || (loff_t) (pos + count) < 0))
goto Einval;
inode = file->f_dentry->d_inode;
- if (inode->i_flock && MANDATORY_LOCK(inode))
- return locks_mandatory_area(read_write == READ ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE, inode, file, pos, count);
- return 0;
+ if (inode->i_flock && MANDATORY_LOCK(inode)) {
+ int retval = locks_mandatory_area(
+ read_write == READ ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE,
+ inode, file, pos, count);
+ if (retval < 0)
+ return retval;
+ }
+ return count > MAX_RW_COUNT ? MAX_RW_COUNT : count;
Einval:
return -EINVAL;
@@ -244,7 +256,8 @@
return -EFAULT;
ret = rw_verify_area(READ, file, pos, count);
- if (!ret) {
+ if (ret >= 0) {
+ count = ret;
ret = security_file_permission (file, MAY_READ);
if (!ret) {
if (file->f_op->read)
@@ -295,7 +308,8 @@
return -EFAULT;
ret = rw_verify_area(WRITE, file, pos, count);
- if (!ret) {
+ if (ret >= 0) {
+ count = ret;
ret = security_file_permission (file, MAY_WRITE);
if (!ret) {
if (file->f_op->write)
@@ -497,7 +511,7 @@
}
ret = rw_verify_area(type, file, pos, tot_len);
- if (ret)
+ if (ret < 0)
goto out;
ret = security_file_permission(file, type == READ ? MAY_READ : MAY_WRITE);
if (ret)
@@ -653,8 +667,9 @@
if (!(in_file->f_mode & FMODE_PREAD))
goto fput_in;
retval = rw_verify_area(READ, in_file, ppos, count);
- if (retval)
+ if (retval < 0)
goto fput_in;
+ count = retval;
retval = security_file_permission (in_file, MAY_READ);
if (retval)
@@ -674,8 +689,9 @@
goto fput_out;
out_inode = out_file->f_dentry->d_inode;
retval = rw_verify_area(WRITE, out_file, &out_file->f_pos, count);
- if (retval)
+ if (retval < 0)
goto fput_out;
+ count = retval;
retval = security_file_permission (out_file, MAY_WRITE);
if (retval)