From 02a4d923e4400a36d340ea12d8058f69ebf3a383 Mon Sep 17 00:00:00 2001 From: Savino Dicanosa Date: Tue, 21 Mar 2023 19:44:02 +0000 Subject: [PATCH] io_uring/rsrc: fix null-ptr-deref in io_file_bitmap_get() When fixed files are unregistered, file_alloc_end and alloc_hint are not cleared. This can later cause a NULL pointer dereference in io_file_bitmap_get() if auto index selection is enabled via IORING_FILE_INDEX_ALLOC: [ 6.519129] BUG: kernel NULL pointer dereference, address: 0000000000000000 [...] [ 6.541468] RIP: 0010:_find_next_zero_bit+0x1a/0x70 [...] [ 6.560906] Call Trace: [ 6.561322] [ 6.561672] io_file_bitmap_get+0x38/0x60 [ 6.562281] io_fixed_fd_install+0x63/0xb0 [ 6.562851] ? __pfx_io_socket+0x10/0x10 [ 6.563396] io_socket+0x93/0xf0 [ 6.563855] ? __pfx_io_socket+0x10/0x10 [ 6.564411] io_issue_sqe+0x5b/0x3d0 [ 6.564914] io_submit_sqes+0x1de/0x650 [ 6.565452] __do_sys_io_uring_enter+0x4fc/0xb20 [ 6.566083] ? __do_sys_io_uring_register+0x11e/0xd80 [ 6.566779] do_syscall_64+0x3c/0x90 [ 6.567247] entry_SYSCALL_64_after_hwframe+0x72/0xdc [...] To fix the issue, set file alloc range and alloc_hint to zero after file tables are freed. Cc: stable@vger.kernel.org Fixes: 4278a0deb1f6 ("io_uring: defer alloc_hint update to io_file_bitmap_set()") Signed-off-by: Savino Dicanosa [axboe: add explicit bitmap == NULL check as well] Signed-off-by: Jens Axboe --- io_uring/filetable.c | 3 +++ io_uring/rsrc.c | 1 + 2 files changed, 4 insertions(+) diff --git a/io_uring/filetable.c b/io_uring/filetable.c index 68dfc6936aa7..b80614e7d605 100644 --- a/io_uring/filetable.c +++ b/io_uring/filetable.c @@ -19,6 +19,9 @@ static int io_file_bitmap_get(struct io_ring_ctx *ctx) unsigned long nr = ctx->file_alloc_end; int ret; + if (!table->bitmap) + return -ENFILE; + do { ret = find_next_zero_bit(table->bitmap, nr, table->alloc_hint); if (ret != nr) diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c index e2bac9f89902..7a43aed8e395 100644 --- a/io_uring/rsrc.c +++ b/io_uring/rsrc.c @@ -794,6 +794,7 @@ void __io_sqe_files_unregister(struct io_ring_ctx *ctx) } #endif io_free_file_tables(&ctx->file_table); + io_file_table_set_alloc_range(ctx, 0, 0); io_rsrc_data_free(ctx->file_data); ctx->file_data = NULL; ctx->nr_user_files = 0;