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authorNadav Amit <namit@vmware.com>2021-08-07 17:13:42 -0700
committerJens Axboe <axboe@kernel.dk>2021-08-08 21:21:11 -0600
commit20c0b380f971e7d48f5d978bc27d827f7eabb21a (patch)
tree502ab1f31055a72f8c56dc43190978fcb1d7915b /fs
parentef98eb0409c31c39ab55ff46b2721c3b4f84c122 (diff)
io_uring: Use WRITE_ONCE() when writing to sq_flags
The compiler should be forbidden from any strange optimization for async writes to user visible data-structures. Without proper protection, the compiler can cause write-tearing or invent writes that would confuse the userspace. However, there are writes to sq_flags which are not protected by WRITE_ONCE(). Use WRITE_ONCE() for these writes. This is purely a theoretical issue. Presumably, any compiler is very unlikely to do such optimizations. Fixes: 75b28affdd6a ("io_uring: allocate the two rings together") Cc: Jens Axboe <axboe@kernel.dk> Cc: Pavel Begunkov <asml.silence@gmail.com> Signed-off-by: Nadav Amit <namit@vmware.com> Link: https://lore.kernel.org/r/20210808001342.964634-3-namit@vmware.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs')
-rw-r--r--fs/io_uring.c13
1 files changed, 9 insertions, 4 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 1093df3977b8..ca064486cb41 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1500,7 +1500,8 @@ static bool __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force)
all_flushed = list_empty(&ctx->cq_overflow_list);
if (all_flushed) {
clear_bit(0, &ctx->check_cq_overflow);
- ctx->rings->sq_flags &= ~IORING_SQ_CQ_OVERFLOW;
+ WRITE_ONCE(ctx->rings->sq_flags,
+ ctx->rings->sq_flags & ~IORING_SQ_CQ_OVERFLOW);
}
if (posted)
@@ -1579,7 +1580,9 @@ static bool io_cqring_event_overflow(struct io_ring_ctx *ctx, u64 user_data,
}
if (list_empty(&ctx->cq_overflow_list)) {
set_bit(0, &ctx->check_cq_overflow);
- ctx->rings->sq_flags |= IORING_SQ_CQ_OVERFLOW;
+ WRITE_ONCE(ctx->rings->sq_flags,
+ ctx->rings->sq_flags | IORING_SQ_CQ_OVERFLOW);
+
}
ocqe->cqe.user_data = user_data;
ocqe->cqe.res = res;
@@ -6804,14 +6807,16 @@ static inline void io_ring_set_wakeup_flag(struct io_ring_ctx *ctx)
{
/* Tell userspace we may need a wakeup call */
spin_lock_irq(&ctx->completion_lock);
- ctx->rings->sq_flags |= IORING_SQ_NEED_WAKEUP;
+ WRITE_ONCE(ctx->rings->sq_flags,
+ ctx->rings->sq_flags | IORING_SQ_NEED_WAKEUP);
spin_unlock_irq(&ctx->completion_lock);
}
static inline void io_ring_clear_wakeup_flag(struct io_ring_ctx *ctx)
{
spin_lock_irq(&ctx->completion_lock);
- ctx->rings->sq_flags &= ~IORING_SQ_NEED_WAKEUP;
+ WRITE_ONCE(ctx->rings->sq_flags,
+ ctx->rings->sq_flags & ~IORING_SQ_NEED_WAKEUP);
spin_unlock_irq(&ctx->completion_lock);
}