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io_uring/memmap: cast nr_pages to size_t before shifting

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If the allocated size exceeds UINT_MAX, then it's necessary to cast
the mr->nr_pages value to size_t to prevent it from overflowing. In
practice this isn't much of a concern as the required memory size will
have been validated upfront, and accounted to the user. And > 4GB sizes
will be necessary to make the lack of a cast a problem, which greatly
exceeds normal user locked_vm settings that are generally in the kb to
mb range. However, if root is used, then accounting isn't done, and
then it's possible to hit this issue.

Link: https://lore.kernel.org/all/6895b298.050a0220.7f033.0059.GAE@google.com/
Cc: stable@vger.kernel.org
Reported-by: syzbot+23727438116feb13df15@syzkaller.appspotmail.com
Fixes: 087f997870 ("io_uring/memmap: implement mmap for regions")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2025-08-08 06:35:14 -06:00
parent 6f02527729
commit 33503c083f
1 changed files with 1 additions and 1 deletions
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2
io_uring/memmap.c
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@ -156,7 +156,7 @@ static int io_region_allocate_pages(struct io_ring_ctx *ctx,
unsigned long mmap_offset)
{
gfp_t gfp = GFP_KERNEL_ACCOUNT | __GFP_ZERO | __GFP_NOWARN;
unsigned long size = mr->nr_pages << PAGE_SHIFT;
size_t size = (size_t) mr->nr_pages << PAGE_SHIFT;
unsigned long nr_allocated;
struct page **pages;
void *p;