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Filename Latest commit message Latest commit date
Jason A. Donenfeld 3faf33a856 random: check for signals after page of pool writes
commit 1ce6c8d68f8ac587f54d0a271ac594d3d51f3efb upstream.

get_random_bytes_user() checks for signals after producing a PAGE_SIZE
worth of output, just like /dev/zero does. write_pool() is doing
basically the same work (actually, slightly more expensive), and so
should stop to check for signals in the same way. Let's also name it
write_pool_user() to match get_random_bytes_user(), so this won't be
misused in the future.

Before this patch, massive writes to /dev/urandom would tie up the
process for an extremely long time and make it unterminatable. After, it
can be successfully interrupted. The following test program can be used
to see this works as intended:

  #include <unistd.h>
  #include <fcntl.h>
  #include <signal.h>
  #include <stdio.h>

  static unsigned char x[~0U];

  static void handle(int) { }

  int main(int argc, char *argv[])
  {
    pid_t pid = getpid(), child;
    int fd;
    signal(SIGUSR1, handle);
    if (!(child = fork())) {
      for (;;)
        kill(pid, SIGUSR1);
    }
    fd = open("/dev/urandom", O_WRONLY);
    pause();
    printf("interrupted after writing %zd bytes\n", write(fd, x, sizeof(x)));
    close(fd);
    kill(child, SIGTERM);
    return 0;
  }

Result before: "interrupted after writing 2147479552 bytes"
Result after: "interrupted after writing 4096 bytes"

Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-06-22 14:11:18 +02:00
arch xtensa: use fallback for random_get_entropy() instead of zero 2022-06-22 14:11:15 +02:00
block block: fix bio_clone_blkg_association() to associate with proper blkcg_gq 2022-06-14 18:11:50 +02:00
certs
crypto random: replace custom notifier chain with standard one 2022-06-22 14:11:13 +02:00
Documentation random: fix sysctl documentation nits 2022-06-22 14:11:14 +02:00
drivers random: check for signals after page of pool writes 2022-06-22 14:11:18 +02:00
fs compat_ioctl: remove /dev/random commands 2022-06-22 14:11:03 +02:00
include random: move randomize_page() into mm where it belongs 2022-06-22 14:11:17 +02:00
init random: handle latent entropy and command line from random_init() 2022-06-22 14:11:17 +02:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2022-06-14 18:11:41 +02:00
kernel timekeeping: Add raw clock fallback for random_get_entropy() 2022-06-22 14:11:15 +02:00
lib random: remove ratelimiting for in-kernel unseeded randomness 2022-06-22 14:11:17 +02:00
LICENSES
mm random: move randomize_page() into mm where it belongs 2022-06-22 14:11:17 +02:00
net tcp: fix tcp_mtup_probe_success vs wrong snd_cwnd 2022-06-14 18:12:03 +02:00
samples
scripts scripts/gdb: change kernel config dumping method 2022-06-14 18:12:02 +02:00
security efi: Do not import certificates from UEFI Secure Boot for T2 Macs 2022-06-14 18:11:44 +02:00
sound ALSA: hda/conexant - Fix loopback issue with CX20632 2022-06-14 18:12:02 +02:00
tools netfilter: nat: really support inet nat without l3 address 2022-06-14 18:11:57 +02:00
usr
virt KVM: Prevent module exit until all VMs are freed 2022-04-15 14:18:27 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS MAINTAINERS: co-maintain random.c 2022-06-22 14:11:05 +02:00
Makefile Linux 5.4.199 2022-06-16 13:23:32 +02:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.