[0/3] Fixes multiple sysctl proc_handler usage error

Message

Nicolas Bouchinet Nov. 12, 2024, 1:13 p.m. UTC

From: Nicolas Bouchinet <[e-mail]>

Hi, while reading sysctl code I encountered two sysctl proc_handler
parameters common errors.

The first one is to declare .data as a different type thant the return of
the used .proc_handler, i.e. using proch_dointvec, thats convert a char
string to signed integers, and storing the result in a .data that is backed
by an unsigned int. User can then write "-1" string, which results in a
different value stored in the .data variable. This can lead to type
conversion errors in branches and thus to potential security issues.

From a quick search using regex and only for proc_dointvec, this seems to
be a pretty common mistake.

The second one is to declare .extra1 or .extra2 values with a .proc_handler
that don't uses them. i.e, declaring .extra1 or .extra2 using proc_dointvec
in order to declare conversion bounds do not work as do_proc_dointvec don't
uses those variables if not explicitly asked.

This patchset corrects three sysctl declaration that are buggy as an
example and is not exhaustive.

Nicolas

Nicolas Bouchinet (3):
  coredump: Fixes core_pipe_limit sysctl proc_handler
  sysctl: Fix underflow value setting risk in vm_table
  tty: ldsic: fix tty_ldisc_autoload sysctl's proc_handler

 drivers/tty/tty_io.c | 2 +-
 fs/coredump.c        | 7 +++++--
 kernel/sysctl.c      | 2 +-
 3 files changed, 7 insertions(+), 4 deletions(-)