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io_uring/fdinfo: grab ctx->uring_lock around io_uring_show_fdinfo() 

Not everything requires locking in there, which is why the 'has_lock'
variable exists. But enough does that it's a bit unwieldy to manage.
Wrap the whole thing in a ->uring_lock trylock, and just return
with no output if we fail to grab it. The existing trylock() will
already have greatly diminished utility/output for the failure case.

This fixes an issue with reading the SQE fields, if the ring is being
actively resized at the same time.

Reported-by: Jann Horn <jannh@google.com>
Fixes: 79cfe9e59c ("io_uring/register: add IORING_REGISTER_RESIZE_RINGS")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
pull/1237/head
Jens Axboe 2025-05-13 15:02:23 -06:00
parent f446c6311e
commit d871198ee4
1 changed files with 25 additions and 23 deletions
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48
io_uring/fdinfo.c
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@ -86,13 +86,8 @@ static inline void napi_show_fdinfo(struct io_ring_ctx *ctx,
}
#endif
/*
* Caller holds a reference to the file already, we don't need to do
* anything else to get an extra reference.
*/
__cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file)
static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
{
struct io_ring_ctx *ctx = file->private_data;
struct io_overflow_cqe *ocqe;
struct io_rings *r = ctx->rings;
struct rusage sq_usage;
@ -106,7 +101,6 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file)
unsigned int sq_entries, cq_entries;
int sq_pid = -1, sq_cpu = -1;
u64 sq_total_time = 0, sq_work_time = 0;
bool has_lock;
unsigned int i;
if (ctx->flags & IORING_SETUP_CQE32)
@ -176,15 +170,7 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file)
seq_printf(m, "\n");
}
/*
* Avoid ABBA deadlock between the seq lock and the io_uring mutex,
* since fdinfo case grabs it in the opposite direction of normal use
* cases. If we fail to get the lock, we just don't iterate any
* structures that could be going away outside the io_uring mutex.
*/
has_lock = mutex_trylock(&ctx->uring_lock);
if (has_lock && (ctx->flags & IORING_SETUP_SQPOLL)) {
if (ctx->flags & IORING_SETUP_SQPOLL) {
struct io_sq_data *sq = ctx->sq_data;
/*
@ -206,7 +192,7 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file)
seq_printf(m, "SqTotalTime:\t%llu\n", sq_total_time);
seq_printf(m, "SqWorkTime:\t%llu\n", sq_work_time);
seq_printf(m, "UserFiles:\t%u\n", ctx->file_table.data.nr);
for (i = 0; has_lock && i < ctx->file_table.data.nr; i++) {
for (i = 0; i < ctx->file_table.data.nr; i++) {
struct file *f = NULL;
if (ctx->file_table.data.nodes[i])
@ -218,7 +204,7 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file)
}
}
seq_printf(m, "UserBufs:\t%u\n", ctx->buf_table.nr);
for (i = 0; has_lock && i < ctx->buf_table.nr; i++) {
for (i = 0; i < ctx->buf_table.nr; i++) {
struct io_mapped_ubuf *buf = NULL;
if (ctx->buf_table.nodes[i])
@ -228,7 +214,7 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file)
else
seq_printf(m, "%5u: <none>\n", i);
}
if (has_lock && !xa_empty(&ctx->personalities)) {
if (!xa_empty(&ctx->personalities)) {
unsigned long index;
const struct cred *cred;
@ -238,7 +224,7 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file)
}
seq_puts(m, "PollList:\n");
for (i = 0; has_lock && i < (1U << ctx->cancel_table.hash_bits); i++) {
for (i = 0; i < (1U << ctx->cancel_table.hash_bits); i++) {
struct io_hash_bucket *hb = &ctx->cancel_table.hbs[i];
struct io_kiocb *req;
@ -247,9 +233,6 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file)
task_work_pending(req->tctx->task));
}
if (has_lock)
mutex_unlock(&ctx->uring_lock);
seq_puts(m, "CqOverflowList:\n");
spin_lock(&ctx->completion_lock);
list_for_each_entry(ocqe, &ctx->cq_overflow_list, list) {
@ -262,4 +245,23 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file)
spin_unlock(&ctx->completion_lock);
napi_show_fdinfo(ctx, m);
}
/*
* Caller holds a reference to the file already, we don't need to do
* anything else to get an extra reference.
*/
__cold void io_uring_show_fdinfo(struct seq_file *m, struct file *file)
{
struct io_ring_ctx *ctx = file->private_data;
/*
* Avoid ABBA deadlock between the seq lock and the io_uring mutex,
* since fdinfo case grabs it in the opposite direction of normal use
* cases.
*/
if (mutex_trylock(&ctx->uring_lock)) {
__io_uring_show_fdinfo(ctx, m);
mutex_unlock(&ctx->uring_lock);
}
}
#endif