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author | Eric Biggers <ebiggers@google.com> | 2020-03-07 18:38:49 -0800 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-03-24 13:27:16 +0100 |
commit | a65cab7d7f05c2061a3e2490257d3086ff3202c6 (patch) | |
tree | 897fff31b7feb585234c26ed50745dbc5cba7e69 /drivers/base | |
parent | 4dbe191c046e71d6ea1ba85365ecb33961b07c4f (diff) | |
download | linux-a65cab7d7f05c2061a3e2490257d3086ff3202c6.tar.bz2 |
libfs: fix infoleak in simple_attr_read()
Reading from a debugfs file at a nonzero position, without first reading
at position 0, leaks uninitialized memory to userspace.
It's a bit tricky to do this, since lseek() and pread() aren't allowed
on these files, and write() doesn't update the position on them. But
writing to them with splice() *does* update the position:
#define _GNU_SOURCE 1
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
int main()
{
int pipes[2], fd, n, i;
char buf[32];
pipe(pipes);
write(pipes[1], "0", 1);
fd = open("/sys/kernel/debug/fault_around_bytes", O_RDWR);
splice(pipes[0], NULL, fd, NULL, 1, 0);
n = read(fd, buf, sizeof(buf));
for (i = 0; i < n; i++)
printf("%02x", buf[i]);
printf("\n");
}
Output:
5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a30
Fix the infoleak by making simple_attr_read() always fill
simple_attr::get_buf if it hasn't been filled yet.
Reported-by: syzbot+fcab69d1ada3e8d6f06b@syzkaller.appspotmail.com
Reported-by: Alexander Potapenko <glider@google.com>
Fixes: acaefc25d21f ("[PATCH] libfs: add simple attribute files")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200308023849.988264-1-ebiggers@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/base')
0 files changed, 0 insertions, 0 deletions