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Subject[patch] remove redundant iov segment check
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The access_ok() and negative length check on each iov segment in function
generic_file_aio_read/write are redundant. They are all already checked
before calling down to these low level generic functions.

Vector I/O (both sync and async) are checked via rw_copy_check_uvector().
For single segment synchronous I/O, the checks are done in various places:
first access_ok() is checked in vfs_read/write, the negative length is
checked in rw_verify_area. For single segment AIO, access_ok() is done
in aio_setup_iocb, and negative length is checked in io_submit_one.

So it's not possible to call down to generic_file_aio_read/write with invalid
iov segment. Patch proposed to delete these redundant code. Also moved
negative length check for single segment AIO into aio_setup_single_vector
to somewhat mirror aio_setup_vectored_rw that they check illegal negative
length. It fits better there too because iocb->aio_nbytes is now double
duty as segment count for vectored AIO, and checking negative length in
the entry point of all AIO isn't very obvious.


Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>


diff -Nurp linux-2.6.19/fs/aio.c linux-2.6.19.ken/fs/aio.c
--- linux-2.6.19/fs/aio.c 2006-11-29 13:57:37.000000000 -0800
+++ linux-2.6.19.ken/fs/aio.c 2006-12-03 17:16:52.000000000 -0800
@@ -1416,6 +1416,8 @@ static ssize_t aio_setup_single_vector(s
kiocb->ki_nr_segs = 1;
kiocb->ki_cur_seg = 0;
kiocb->ki_nbytes = kiocb->ki_left;
+ if (unlikely((ssize_t) kiocb->ki_nbytes < 0))
+ return -EINVAL;
return 0;
}

@@ -1560,8 +1562,7 @@ int fastcall io_submit_one(struct kioctx
/* prevent overflows */
if (unlikely(
(iocb->aio_buf != (unsigned long)iocb->aio_buf) ||
- (iocb->aio_nbytes != (size_t)iocb->aio_nbytes) ||
- ((ssize_t)iocb->aio_nbytes < 0)
+ (iocb->aio_nbytes != (size_t)iocb->aio_nbytes)
)) {
pr_debug("EINVAL: io_submit: overflow check\n");
return -EINVAL;
diff -Nurp linux-2.6.19/mm/filemap.c linux-2.6.19.ken/mm/filemap.c
--- linux-2.6.19/mm/filemap.c 2006-11-29 13:57:37.000000000 -0800
+++ linux-2.6.19.ken/mm/filemap.c 2006-12-03 17:16:10.000000000 -0800
@@ -1143,29 +1143,9 @@ generic_file_aio_read(struct kiocb *iocb
struct file *filp = iocb->ki_filp;
ssize_t retval;
unsigned long seg;
- size_t count;
+ size_t count = iocb->ki_left;
loff_t *ppos = &iocb->ki_pos;

- count = 0;
- for (seg = 0; seg < nr_segs; seg++) {
- const struct iovec *iv = &iov[seg];
-
- /*
- * If any segment has a negative length, or the cumulative
- * length ever wraps negative then return -EINVAL.
- */
- count += iv->iov_len;
- if (unlikely((ssize_t)(count|iv->iov_len) < 0))
- return -EINVAL;
- if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
- continue;
- if (seg == 0)
- return -EFAULT;
- nr_segs = seg;
- count -= iv->iov_len; /* This segment is no good */
- break;
- }
-
/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
if (filp->f_flags & O_DIRECT) {
loff_t size;
@@ -2228,32 +2208,11 @@ __generic_file_aio_write_nolock(struct k
size_t ocount; /* original count */
size_t count; /* after file limit checks */
struct inode *inode = mapping->host;
- unsigned long seg;
loff_t pos;
ssize_t written;
ssize_t err;

- ocount = 0;
- for (seg = 0; seg < nr_segs; seg++) {
- const struct iovec *iv = &iov[seg];
-
- /*
- * If any segment has a negative length, or the cumulative
- * length ever wraps negative then return -EINVAL.
- */
- ocount += iv->iov_len;
- if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
- return -EINVAL;
- if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
- continue;
- if (seg == 0)
- return -EFAULT;
- nr_segs = seg;
- ocount -= iv->iov_len; /* This segment is no good */
- break;
- }
-
- count = ocount;
+ count = ocount = iocb->ki_left;
pos = *ppos;

vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
-
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