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Kernel: Correctly interpret ioctl's FIONBIO user value

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Values in `ioctl` are given through a pointer, but ioctl's FIONBIO
implementation was interpreting this pointer as an integer directly.
This meant that programs using `ioctl` to set a file descriptor in
blocking mode met with incorrect behavior: they passed a non-null
pointer pointing to a value of 0, but the kernel interpreted the pointer
as a non-zero integer, thus making the file non-blocking.

This commit fixes this behavior by reading the value from the userspace
pointer and using that to set the non-blocking flag on the file
descriptor.

This bug was found while trying to run the openssl tool on serenity,
which used `ioctl` to ensure newly-created sockets are in blocking mode.
This commit is contained in:
Rodrigo Tobar 2021-10-11 21:47:21 +08:00 • committed by Brian Gianforcaro
parent 01a716d529
commit bf4e536f00
1 changed files with 4 additions and 1 deletions
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5
Kernel/Syscalls/ioctl.cpp
View file

@ -4,6 +4,7 @@
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Userspace.h>
#include <Kernel/FileSystem/OpenFileDescription.h>
#include <Kernel/Process.h>
#include <LibC/sys/ioctl_numbers.h>
@ -15,7 +16,9 @@ KResultOr<FlatPtr> Process::sys$ioctl(int fd, unsigned request, FlatPtr arg)
VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this)
auto description = TRY(fds().open_file_description(fd));
if (request == FIONBIO) {
description->set_blocking(arg == 0);
int non_blocking;
TRY(copy_from_user(&non_blocking, Userspace<const int*>(arg)));
description->set_blocking(non_blocking == 0);
return KSuccess;
}
return description->file().ioctl(*description, request, arg);