[PATCH 1/1] lib/iov_iter: fix import_iovec_ubuf iovec management

[PATCH 1/1] lib/iov_iter: fix import_iovec_ubuf iovec management

[Pavel Begunkov]

import_iovec() says that it should always be fine to kfree the iovec
returned in @iovp regardless of the error code. __import_iovec_ubuf()
never reallocates it and thus should clear the pointer even in cases
when copy_iovec_*() fail.

Cc: stable@vger.kernel.org
Fixes: 3b2deb0e46da9 ("iov_iter: import single vector iovecs as ITER_UBUF")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 lib/iov_iter.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 9ec806f989f25..65f550cb5081b 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1428,6 +1428,8 @@ static ssize_t __import_iovec_ubuf(int type, const struct iovec __user *uvec,
 	struct iovec *iov = *iovp;
 	ssize_t ret;
 
+	*iovp = NULL;
+
 	if (compat)
 		ret = copy_compat_iovec_from_user(iov, uvec, 1);
 	else
@@ -1438,7 +1440,6 @@ static ssize_t __import_iovec_ubuf(int type, const struct iovec __user *uvec,
 	ret = import_ubuf(type, iov->iov_base, iov->iov_len, i);
 	if (unlikely(ret))
 		return ret;
-	*iovp = NULL;
 	return i->count;
 }
 
-- 
2.47.1

Re: [PATCH 1/1] lib/iov_iter: fix import_iovec_ubuf iovec management

[Jens Axboe]

On 1/31/25 7:13 AM, Pavel Begunkov wrote:
> import_iovec() says that it should always be fine to kfree the iovec
> returned in @iovp regardless of the error code. __import_iovec_ubuf()
> never reallocates it and thus should clear the pointer even in cases
> when copy_iovec_*() fail.

Looks good to me:

Reviewed-by: Jens Axboe <axboe@kernel.dk>

-- 
Jens Axboe

Re: [PATCH 1/1] lib/iov_iter: fix import_iovec_ubuf iovec management

[Pavel Begunkov]

On 1/31/25 14:13, Pavel Begunkov wrote:
> import_iovec() says that it should always be fine to kfree the iovec
> returned in @iovp regardless of the error code. __import_iovec_ubuf()
> never reallocates it and thus should clear the pointer even in cases
> when copy_iovec_*() fail.

To be fair, all callers I checked don't look at the returned iovec
if import_iovec*() fails, but I didn't track down all of them.

-- 
Pavel Begunkov

Re: [PATCH 1/1] lib/iov_iter: fix import_iovec_ubuf iovec management

[Jens Axboe]

On 1/31/25 9:06 AM, Pavel Begunkov wrote:
> On 1/31/25 14:13, Pavel Begunkov wrote:
>> import_iovec() says that it should always be fine to kfree the iovec
>> returned in @iovp regardless of the error code. __import_iovec_ubuf()
>> never reallocates it and thus should clear the pointer even in cases
>> when copy_iovec_*() fail.
> 
> To be fair, all callers I checked don't look at the returned iovec
> if import_iovec*() fails, but I didn't track down all of them.

Yep I also checked too and didn't spot any issues from this, but it's
still prudent to clean it up.

-- 
Jens Axboe