tree 4618e519b2d1d640c0da7db72497a7a82bd6940b
parent d1fbc465c6625b1f84378c603c335f6f794a0ee1
author Jack Rosenthal <jrosenth@chromium.org> 1617984194 -0600
committer Nico Huber <nico.h@gmx.de> 1674348918 +0000

cli_classic: prevent corruption of flash when stdout/stderr is closed

While it's not posixly-correct, it's possible that a user, script, or
application may attempt to start flashrom with stdout or stderr
closed.  It's possible that we'll get a file descriptor of 1 or 2 when
opening a flash device (such as Linux MTD), and flashrom will send
garbage debug logs to the flash:

  # bash -c "exec >&- flashrom ..."

  Observed corruption:
  43 40 45 42 45 44 00 00 00 00 00 00 01 00 00 00 |C@EBED..........|
  00 02 00 00 63 65 73 73 66 75 6c 6c 79 0a 46 6f |....cessfully.Fo|
  75 6e 64 20 50 72 6f 67 72 61 6d 6d 65 72 20 66 |und Programmer f|
  6c 61 73 68 20 63 68 69 70 20 22 4f 70 61 71 75 |lash chip "Opaqu|
  65 20 66 6c 61 73 68 20 63 68 69 70 22 20 28 38 |e flash chip" (8|
  31 39 32 20 6b 42 2c 20 50 72 6f 67 72 61 6d 6d |192 kB, Programm|
  65 72 2d 73 70 65 63 69 66 69 63 29 20 6d 61 70 |er-specific) map|
  70 65 64 20 61 74 20 70 68 79 73 69 63 61 6c 20 |ped at physical |
  61 64 64 72 65 73 73 20 30 78 30 30 30 30 30 30 |address 0x000000|
  30 30 2e 0a ff ff ff ff ff ff ff ff ff ff ff ff |00..............|
  ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
  ...

While for most applications, closing stdout or stderr would just lead
to obsure bugs, for flashrom, we should have extra safety guards, as
this could mean that we might be bricking a device instead.

Add a basic safety check.

Signed-off-by: Jack Rosenthal <jrosenth@chromium.org>
Change-Id: I751c9dd88ad1d30283b94bd2185b4f8f25569c8f
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/52215
Original-Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72166
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>