[PATCH 1/2] iov_iter: mark truncated iters

From: Pavel Begunkov
Date: Mon Aug 09 2021 - 07:53:20 EST


Track if an iterator has ever been truncated. This will be used to
mitigate revert-truncate problems.

Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
include/linux/uio.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 82c3c3e819e0..61b8d312d13a 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -30,6 +30,7 @@ enum iter_type {
struct iov_iter {
u8 iter_type;
bool data_source;
+ bool truncated;
size_t iov_offset;
size_t count;
union {
@@ -254,8 +255,10 @@ static inline void iov_iter_truncate(struct iov_iter *i, u64 count)
* conversion in assignement is by definition greater than all
* values of size_t, including old i->count.
*/
- if (i->count > count)
+ if (i->count > count) {
i->count = count;
+ i->truncated = true;
+ }
}

/*
--
2.32.0