Karl Mehltretter c2e3aadc8f ARM: 9475/1: entry: use byte load for KASAN VMAP stack shadow
commit 77a1f6883d upstream.

Commit 44e9a3bb76 ("ARM: 9430/1: entry: Do a dummy read from
VMAP shadow") added a dummy read from the KASAN VMAP stack shadow in
__switch_to(). The read uses ldr, but the KASAN shadow address is
byte-granular and is not guaranteed to be word aligned.

ARMv5 faults unaligned word loads. With CONFIG_KASAN_VMALLOC and
CONFIG_VMAP_STACK enabled, ARM926/VersatilePB crashes in __switch_to()
with an alignment exception before reaching init.

Use ldrb for the dummy shadow access. The code only needs to fault in the
shadow mapping if the stack shadow is missing, so a byte load is sufficient
and matches the granularity of KASAN shadow memory.

Fixes: 44e9a3bb76 ("ARM: 9430/1: entry: Do a dummy read from VMAP shadow")
Cc: stable@vger.kernel.org # v6.13+
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2026-06-19 13:39:33 +02:00
2026-05-23 13:03:09 +02:00
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2026-05-23 13:03:09 +02:00
2026-06-01 17:43:16 +02:00
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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.
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