6.1-stable review patch. If anyone has any objections, please let me know.
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From: Jens Axboe axboe@kernel.dk
Commit 06fe9b1df1086b42718d632aa57e8f7cd1a66a21 upstream.
If IORING_FEAT_SINGLE_MMAP is ignored, as can happen if an application uses an ancient liburing or does setup manually, then 3 mmap's are required to map the ring into userspace. The kernel will still have collapsed the mappings, however userspace may ask for mapping them individually. If so, then we should not use the full number of ring pages, as it may exceed the partial mapping. Doing so will yield an -EFAULT from vm_insert_pages(), as we pass in more pages than what the application asked for.
Cap the number of pages to match what the application asked for, for the particular mapping operation.
Reported-by: Lucas Mülling lmulling@proton.me Link: https://github.com/axboe/liburing/issues/1157 Fixes: 3ab1db3c6039 ("io_uring: get rid of remap_pfn_range() for mapping rings/sqes") Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/io_uring.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -3237,6 +3237,7 @@ static __cold int io_uring_mmap(struct f struct io_ring_ctx *ctx = file->private_data; size_t sz = vma->vm_end - vma->vm_start; long offset = vma->vm_pgoff << PAGE_SHIFT; + unsigned int npages; unsigned long pfn; void *ptr;
@@ -3247,8 +3248,8 @@ static __cold int io_uring_mmap(struct f switch (offset & IORING_OFF_MMAP_MASK) { case IORING_OFF_SQ_RING: case IORING_OFF_CQ_RING: - return io_uring_mmap_pages(ctx, vma, ctx->ring_pages, - ctx->n_ring_pages); + npages = min(ctx->n_ring_pages, (sz + PAGE_SIZE - 1) >> PAGE_SHIFT); + return io_uring_mmap_pages(ctx, vma, ctx->ring_pages, npages); case IORING_OFF_SQES: return io_uring_mmap_pages(ctx, vma, ctx->sqe_pages, ctx->n_sqe_pages);