From: Jens Axboe Date: Wed, 30 Apr 2025 13:17:17 +0000 (-0600) Subject: io_uring/fdinfo: annotate racy sq/cq head/tail reads X-Git-Tag: io_uring-6.15-20250502^0 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=f024d3a8ded0d8d2129ae123d7a5305c29ca44ce;p=linux-block.git io_uring/fdinfo: annotate racy sq/cq head/tail reads syzbot complains about the cached sq head read, and it's totally right. But we don't need to care, it's just reading fdinfo, and reading the CQ or SQ tail/head entries are known racy in that they are just a view into that very instant and may of course be outdated by the time they are reported. Annotate both the SQ head and CQ tail read with data_race() to avoid this syzbot complaint. Link: https://lore.kernel.org/io-uring/6811f6dc.050a0220.39e3a1.0d0e.GAE@google.com/ Reported-by: syzbot+3e77fd302e99f5af9394@syzkaller.appspotmail.com Signed-off-by: Jens Axboe --- diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c index f60d0a9d505e..9414ca6d101c 100644 --- a/io_uring/fdinfo.c +++ b/io_uring/fdinfo.c @@ -123,11 +123,11 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file) seq_printf(m, "SqMask:\t0x%x\n", sq_mask); seq_printf(m, "SqHead:\t%u\n", sq_head); seq_printf(m, "SqTail:\t%u\n", sq_tail); - seq_printf(m, "CachedSqHead:\t%u\n", ctx->cached_sq_head); + seq_printf(m, "CachedSqHead:\t%u\n", data_race(ctx->cached_sq_head)); seq_printf(m, "CqMask:\t0x%x\n", cq_mask); seq_printf(m, "CqHead:\t%u\n", cq_head); seq_printf(m, "CqTail:\t%u\n", cq_tail); - seq_printf(m, "CachedCqTail:\t%u\n", ctx->cached_cq_tail); + seq_printf(m, "CachedCqTail:\t%u\n", data_race(ctx->cached_cq_tail)); seq_printf(m, "SQEs:\t%u\n", sq_tail - sq_head); sq_entries = min(sq_tail - sq_head, ctx->sq_entries); for (i = 0; i < sq_entries; i++) {