x86/alternatives: Remove faulty optimization
authorJosh Poimboeuf <jpoimboe@kernel.org>
Tue, 5 Sep 2023 05:04:54 +0000 (22:04 -0700)
committerBorislav Petkov (AMD) <bp@alien8.de>
Fri, 22 Sep 2023 16:52:39 +0000 (18:52 +0200)
commit4ba89dd6ddeca2a733bdaed7c9a5cbe4e19d9124
treeeaf1884b908beb6032fc97e35e925c969e5c73a5
parentce9ecca0238b140b88f43859b211c9fdfd8e5b70
x86/alternatives: Remove faulty optimization

The following commit

  095b8303f383 ("x86/alternative: Make custom return thunk unconditional")

made '__x86_return_thunk' a placeholder value.  All code setting
X86_FEATURE_RETHUNK also changes the value of 'x86_return_thunk'.  So
the optimization at the beginning of apply_returns() is dead code.

Also, before the above-mentioned commit, the optimization actually had a
bug It bypassed __static_call_fixup(), causing some raw returns to
remain unpatched in static call trampolines.  Thus the 'Fixes' tag.

Fixes: d2408e043e72 ("x86/alternative: Optimize returns patching")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/16d19d2249d4485d8380fb215ffaae81e6b8119e.1693889988.git.jpoimboe@kernel.org
arch/x86/kernel/alternative.c