platform/x86: hp-bioscfg: fix heap OOB read on empty password write

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validate_password_input() computes length = strlen(buf) and then
checks buf[length - 1] to strip a trailing newline, without checking
that length is nonzero first. Writing an empty string (a bare '\n')
to current_password or new_password gives length == 0, and
buf[length - 1] reads buf[-1], one byte before the heap allocation
holding the copied input.

KASAN confirms this directly:

  BUG: KASAN: slab-out-of-bounds in store_password_instance.constprop.0+0x223/0x2a0 [hp_bioscfg]
  Read of size 1 at addr ffff88811bd8da9f by task sh/13740
  ...
  store_password_instance.constprop.0+0x223/0x2a0 [hp_bioscfg]
  current_password_store+0x14/0x20 [hp_bioscfg]
  ...
  The buggy address is located 23 bytes to the right of
  allocated 8-byte region [ffff88811bd8da80, ffff88811bd8da88)

Reproduced identically via new_password_store. Execution continues
past the bad read (the garbage byte only affects whether "length" is
decremented by one), so the write completes and returns success; this
is a pure information read past the buffer, not a crash, but it is
still an out-of-bounds access KASAN correctly flags.

Fix by only checking buf[length - 1] when length is nonzero.

Fixes: 8646a3b5ee ("platform/x86: hp-bioscfg: passwdobj-attributes")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
Link: https://patch.msgid.link/20260812111829.172273-4-meatuni001@gmail.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

...

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Muhammad Bilal 2026-08-12 16:18:23 +05:00 • committed by Ilpo Järvinen

parent a7508c7959

commit 2b2ec354f9

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drivers/platform/x86/hp/hp-bioscfg/passwdobj-attributes.c

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