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c=relaxed/simple; d=kernel.org; s=k20201202; t=1686757971; bh=A8TF2ckDAIr4008OG16ynqI8vPNCnEPAU4BPRdH58lk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HKuxnUbj/uowyKcgmYurVBwnX5CC+yfvHstHH3hviyfohLiqu0HWzZC4jKpThsgik +uYpg9wgh9e107P8gTDVX7mulbhtow0NmULW10beniC4op0IhoG204ZtTZzWAAn9xj Z6XAcTFhbpBAQCq4B9FfYrY1dFdsrt50HURIgQSuWgsgSWwE3wmo2jxGSAyLkzdvnt E7PsSlVy2SlwzWQ+L+GhRppjXKD9MQ1Da/aboYWbxLXQk5PYHAXaUbjB/kIVFMbP5l eC9z2EgXobSvIxNufUd0Z4ztDzaOHHcLw4F1XxU07ctryWe4kP5Lwn4Ir6pSeujQio NfhS4eaAMR9Xg== From: Lee Jones To: lee@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH 1/1] x86/mm/KASLR: Store pud_page_tramp into entry rather than page Date: Wed, 14 Jun 2023 16:52:10 +0100 Message-ID: <20230614155223.905222-2-lee@kernel.org> X-Mailer: git-send-email 2.41.0.162.gfafddb0af9-goog In-Reply-To: <20230614155223.905222-1-lee@kernel.org> References: <20230614155223.905222-1-lee@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 3CC1310000F X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: m1zit8sgg9nsrj8r81mtk4n8py4y8oow X-HE-Tag: 1686757972-352570 X-HE-Meta: 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 XVUBrZhf Lj73gnRZu+vHub+vMowsw5T6w1mArAAqCVI2Zx2qi+c+szN0Yfcy4/Ud1+NZ0levk6F6g3HRCAamsTf58bHx0i6kH6fFweI0lxA2eaCQtXEbZLiXyGv62/AhDt8daHiCIJLQBfGJHxAsUWeySTQDUK8PS9UR61Wgk+9qo35W0x858KviDUQ9rhbB2Hjjv1pIlyRvUlkWgv1zkeephOd5s66mn33xGOaMQ1XIf/Fb5mgCGw1FYN0YGvKX+LKxkiZ/A16gJREf6Bm/o+noVUToCx7J2L/qWrX/EPrHN6L5Gbocx14hb+ncXQm4e4YMvYDnPDV2Wi4AfhTxE/E4XN5NUpQlywv+7RS/TiMynVXqvPqy64RDUAECfry3yreruqPeOz9Yjte2RTFdQgeAHDWoWvE3Epw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: set_pgd() expects to be passed whole pages to operate on, whereas trampoline_pgd_entry is, as the name suggests, an entry. The ramifications for using set_pgd() here are that the following thread of execution will not only place the suggested value into the trampoline_pgd_entry (8-Byte globally stored [.bss]) variable, PTI will also attempt to replicate that value into the non-existent neighboring user page (located +4k away), leading to the corruption of other global [.bss] stored variables. Suggested-by: Dave Hansen Signed-off-by: Lee Jones --- arch/x86/mm/kaslr.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index 557f0fe25dff4..ee6f22f3385b6 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -175,7 +175,7 @@ void __meminit init_trampoline_kaslr(void) set_pgd(&trampoline_pgd_entry, __pgd(_KERNPG_TABLE | __pa(p4d_page_tramp))); } else { - set_pgd(&trampoline_pgd_entry, - __pgd(_KERNPG_TABLE | __pa(pud_page_tramp))); + trampoline_pgd_entry = + __pgd(_KERNPG_TABLE | __pa(pud_page_tramp)); } } -- 2.41.0.162.gfafddb0af9-goog