Date:	Thu, 11 Mar 2010 11:06:07 -0500
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Michael Tokarev <mjt@....msk.ru>
Cc:	linux-aio@...ck.org, Linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: aio: compat_ioctl issue?

Michael Tokarev <mjt@....msk.ru> writes:

> Michael Tokarev wrote:
>> Jeff Moyer wrote:
>> []
>>>>>> I just come across a situation (next in a long row :)
>>>>>> when on x86, 32bit userspace does not work with 64bit
>>>>>> kernel.  This time this is about aio requests.
>>> [snip]
> []
>>> Could you maybe print out the values that are passed to io_getevents?
>> 
>> They were in my first email, here it goes again:
>> 
>> io_submit: lio_opcode=7 reqprio=0 iov=0x9cd7018{0xf5599000,4096}, niov=1, offset=0
>> io_getevents: expected 4096 got -22 (EINVAL)
>> 
>> This is what gets passed to libaio -- strace here
>> does not decode the arguments unfortunately.
> []
>> My *guess* is that it handles read/write correctly but
>> does not properly handle preadv/pwritev (opcode=7 is
>> IO_CMD_PREADV as far as I can see).  That'll explain
>> my "testcase" with Oracle which does not use preadv.
>
> Actually, looking at the code in fs/compat.c, I don't see
> where it converts iovecs.  Yes it converts iocbs, but for
> readv/writev it also needs to convert iovecs.  Oh well,
> that expects to be quite painful... :(

Yeah, whoops.  I built the libaio test harness using -m32 and this patch
works for me.  Would you mind giving it a try?

Thanks,
Jeff

diff --git a/fs/aio.c b/fs/aio.c
index 1cf12b3..5a38805 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -36,6 +36,7 @@
 #include <linux/blkdev.h>
 #include <linux/mempool.h>
 #include <linux/hash.h>
+#include <linux/compat.h>
 
 #include <asm/kmap_types.h>
 #include <asm/uaccess.h>
@@ -1384,13 +1385,20 @@ static ssize_t aio_fsync(struct kiocb *iocb)
 	return ret;
 }
 
-static ssize_t aio_setup_vectored_rw(int type, struct kiocb *kiocb)
+static ssize_t aio_setup_vectored_rw(int type, struct kiocb *kiocb, bool compat)
 {
 	ssize_t ret;
 
-	ret = rw_copy_check_uvector(type, (struct iovec __user *)kiocb->ki_buf,
-				    kiocb->ki_nbytes, 1,
-				    &kiocb->ki_inline_vec, &kiocb->ki_iovec);
+	if (compat)
+		ret = compat_rw_copy_check_uvector(type,
+				(struct compat_iovec __user *)kiocb->ki_buf,
+				kiocb->ki_nbytes, 1, &kiocb->ki_inline_vec,
+				&kiocb->ki_iovec);
+	else
+		ret = rw_copy_check_uvector(type,
+				(struct iovec __user *)kiocb->ki_buf,
+				kiocb->ki_nbytes, 1, &kiocb->ki_inline_vec,
+				&kiocb->ki_iovec);
 	if (ret < 0)
 		goto out;
 
@@ -1420,7 +1428,7 @@ static ssize_t aio_setup_single_vector(struct kiocb *kiocb)
  *	Performs the initial checks and aio retry method
  *	setup for the kiocb at the time of io submission.
  */
-static ssize_t aio_setup_iocb(struct kiocb *kiocb)
+static ssize_t aio_setup_iocb(struct kiocb *kiocb, bool compat)
 {
 	struct file *file = kiocb->ki_filp;
 	ssize_t ret = 0;
@@ -1469,7 +1477,7 @@ static ssize_t aio_setup_iocb(struct kiocb *kiocb)
 		ret = security_file_permission(file, MAY_READ);
 		if (unlikely(ret))
 			break;
-		ret = aio_setup_vectored_rw(READ, kiocb);
+		ret = aio_setup_vectored_rw(READ, kiocb, compat);
 		if (ret)
 			break;
 		ret = -EINVAL;
@@ -1483,7 +1491,7 @@ static ssize_t aio_setup_iocb(struct kiocb *kiocb)
 		ret = security_file_permission(file, MAY_WRITE);
 		if (unlikely(ret))
 			break;
-		ret = aio_setup_vectored_rw(WRITE, kiocb);
+		ret = aio_setup_vectored_rw(WRITE, kiocb, compat);
 		if (ret)
 			break;
 		ret = -EINVAL;
@@ -1548,7 +1556,8 @@ static void aio_batch_free(struct hlist_head *batch_hash)
 }
 
 static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
-			 struct iocb *iocb, struct hlist_head *batch_hash)
+			 struct iocb *iocb, struct hlist_head *batch_hash,
+			 bool compat)
 {
 	struct kiocb *req;
 	struct file *file;
@@ -1609,7 +1618,7 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
 	req->ki_left = req->ki_nbytes = iocb->aio_nbytes;
 	req->ki_opcode = iocb->aio_lio_opcode;
 
-	ret = aio_setup_iocb(req);
+	ret = aio_setup_iocb(req, compat);
 
 	if (ret)
 		goto out_put_req;
@@ -1637,20 +1646,8 @@ out_put_req:
 	return ret;
 }
 
-/* sys_io_submit:
- *	Queue the nr iocbs pointed to by iocbpp for processing.  Returns
- *	the number of iocbs queued.  May return -EINVAL if the aio_context
- *	specified by ctx_id is invalid, if nr is < 0, if the iocb at
- *	*iocbpp[0] is not properly initialized, if the operation specified
- *	is invalid for the file descriptor in the iocb.  May fail with
- *	-EFAULT if any of the data structures point to invalid data.  May
- *	fail with -EBADF if the file descriptor specified in the first
- *	iocb is invalid.  May fail with -EAGAIN if insufficient resources
- *	are available to queue any iocbs.  Will return 0 if nr is 0.  Will
- *	fail with -ENOSYS if not implemented.
- */
-SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
-		struct iocb __user * __user *, iocbpp)
+long do_io_submit(aio_context_t ctx_id, long nr,
+		  struct iocb __user *__user * iocbpp, bool compat)
 {
 	struct kioctx *ctx;
 	long ret = 0;
@@ -1687,7 +1684,7 @@ SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
 			break;
 		}
 
-		ret = io_submit_one(ctx, user_iocb, &tmp, batch_hash);
+		ret = io_submit_one(ctx, user_iocb, &tmp, batch_hash, compat);
 		if (ret)
 			break;
 	}
@@ -1696,6 +1693,24 @@ SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
 	put_ioctx(ctx);
 	return i ? i : ret;
 }
+		  
+/* sys_io_submit:
+ *	Queue the nr iocbs pointed to by iocbpp for processing.  Returns
+ *	the number of iocbs queued.  May return -EINVAL if the aio_context
+ *	specified by ctx_id is invalid, if nr is < 0, if the iocb at
+ *	*iocbpp[0] is not properly initialized, if the operation specified
+ *	is invalid for the file descriptor in the iocb.  May fail with
+ *	-EFAULT if any of the data structures point to invalid data.  May
+ *	fail with -EBADF if the file descriptor specified in the first
+ *	iocb is invalid.  May fail with -EAGAIN if insufficient resources
+ *	are available to queue any iocbs.  Will return 0 if nr is 0.  Will
+ *	fail with -ENOSYS if not implemented.
+ */
+SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
+		struct iocb __user * __user *, iocbpp)
+{
+	return do_io_submit(ctx_id, nr, iocbpp, 0);
+}
 
 /* lookup_kiocb
  *	Finds a given iocb for cancellation.
diff --git a/fs/compat.c b/fs/compat.c
index 00d90c2..340f20d 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -567,6 +567,61 @@ out:
 	return ret;
 }
 
+/* A write operation does a read from user space and vice versa */
+#define vrfy_dir(type) ((type) == READ ? VERIFY_WRITE : VERIFY_READ)
+
+ssize_t compat_rw_copy_check_uvector(int type,
+		const struct compat_iovec __user *uiov32, unsigned long niov,
+		unsigned long fast_segs, struct iovec *fast_pointer,
+		struct iovec **ret_pointer)
+{
+	ssize_t tot_len = 0;
+	struct iovec *kiov = fast_pointer;
+
+	if (niov == 0)
+		goto out;
+	if (niov > UIO_MAXIOV) {
+		tot_len = -EINVAL;
+		goto out;
+	}
+	if (niov > fast_segs) {
+		kiov = kmalloc(niov*sizeof(struct iovec), GFP_KERNEL);
+		if (kiov == NULL) {
+			tot_len = -ENOMEM;
+			goto out;
+		}
+		*ret_pointer = kiov;
+	}
+
+	while (niov > 0) {
+		compat_uptr_t buf;
+		compat_size_t len;
+
+		if (get_user(len, &uiov32->iov_len) ||
+		   get_user(buf, &uiov32->iov_base)) {
+			tot_len = -EFAULT;
+			goto out;
+		}
+		if (len < 0 || (tot_len + len < tot_len)) {
+			tot_len = -EINVAL;
+			goto out;
+		}
+		if (!access_ok(vrfy_dir(type), buf, len)) {
+			tot_len = -EFAULT;
+			goto out;
+		}
+		tot_len += len;
+		kiov->iov_base = compat_ptr(buf);
+		kiov->iov_len = (__kernel_size_t) len;
+		uiov32++;
+		kiov++;
+		niov--;
+	}
+
+out:
+	return tot_len;
+}
+
 static inline long
 copy_iocb(long nr, u32 __user *ptr32, struct iocb __user * __user *ptr64)
 {
@@ -599,7 +654,7 @@ compat_sys_io_submit(aio_context_t ctx_id, int nr, u32 __user *iocb)
 	iocb64 = compat_alloc_user_space(nr * sizeof(*iocb64));
 	ret = copy_iocb(nr, iocb, iocb64);
 	if (!ret)
-		ret = sys_io_submit(ctx_id, nr, iocb64);
+		ret = do_io_submit(ctx_id, nr, iocb64, 1);
 	return ret;
 }
 
diff --git a/include/linux/aio.h b/include/linux/aio.h
index 811dbb3..54b6ef8 100644
--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -212,6 +212,8 @@ extern void kick_iocb(struct kiocb *iocb);
 extern int aio_complete(struct kiocb *iocb, long res, long res2);
 struct mm_struct;
 extern void exit_aio(struct mm_struct *mm);
+extern long do_io_submit(aio_context_t ctx_id, long nr,
+			 struct iocb __user *__user * iocbpp, bool compat);
 #else
 static inline ssize_t wait_on_sync_kiocb(struct kiocb *iocb) { return 0; }
 static inline int aio_put_req(struct kiocb *iocb) { return 0; }
@@ -219,6 +221,9 @@ static inline void kick_iocb(struct kiocb *iocb) { }
 static inline int aio_complete(struct kiocb *iocb, long res, long res2) { return 0; }
 struct mm_struct;
 static inline void exit_aio(struct mm_struct *mm) { }
+static inline long do_io_submit(aio_context_t ctx_id, long nr,
+				struct iocb __user * __user * iocbpp,
+				bool compat) { }
 #endif /* CONFIG_AIO */
 
 static inline struct kiocb *list_kiocb(struct list_head *h)
diff --git a/include/linux/compat.h b/include/linux/compat.h
index ef68119..8251f61 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -353,5 +353,9 @@ asmlinkage long compat_sys_newfstatat(unsigned int dfd, char __user * filename,
 asmlinkage long compat_sys_openat(unsigned int dfd, const char __user *filename,
 				  int flags, int mode);
 
+extern ssize_t compat_rw_copy_check_uvector(int type,
+		const struct compat_iovec __user *uiov32, unsigned long niov,
+		unsigned long fast_segs, struct iovec *fast_pointer,
+		struct iovec **ret_pointer);
 #endif /* CONFIG_COMPAT */
 #endif /* _LINUX_COMPAT_H */
--
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