parisc: Revise gateway LWS calls to probe user read access

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commit f6334f4ae9 upstream.

We use load and stbys,e instructions to trigger memory reference
interruptions without writing to memory. Because of the way read
access support is implemented, read access interruptions are only
triggered at privilege levels 2 and 3. The kernel and gateway
page execute at privilege level 0, so this code never triggers
a read access interruption. Thus, it is currently possible for
user code to execute a LWS compare and swap operation at an
address that is read protected at privilege level 3 (PRIV_USER).

Fix this by probing read access rights at privilege level 3 and
branching to lws_fault if access isn't allowed.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org # v5.12+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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John David Anglin 2025-07-25 12:12:14 -04:00 • committed by Greg Kroah-Hartman

parent f410ef9a03

commit bc0a24c24c

1 changed files with 21 additions and 9 deletions

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arch/parisc/kernel/syscall.S

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