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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]  <TASK>
[    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: 4278a0deb1 ("io_uring: defer alloc_hint update to io_file_bitmap_set()")
Signed-off-by: Savino Dicanosa <sd7.dev@pm.me>
[axboe: add explicit bitmap == NULL check as well]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Savino Dicanosa 2023-03-21 19:44:02 +00:00 committed by Jens Axboe
parent 74e2e17ee1
commit 02a4d923e4
2 changed files with 4 additions and 0 deletions
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3
io_uring/filetable.c
View File

@ -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)

1
io_uring/rsrc.c
View File

@ -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;