From: Russell Currey <ruscur@russell.cc> To: linuxppc-dev@lists.ozlabs.org Cc: mikey@neuling.org, kernel-hardening@lists.openwall.com, Russell Currey <ruscur@russell.cc>, npiggin@gmail.com Subject: [PATCH v2 2/3] powerpc/lib: Refactor __patch_instruction() to use __put_user_asm() Date: Mon, 10 Dec 2018 18:00:43 +1100 [thread overview] Message-ID: <20181210070044.27503-3-ruscur@russell.cc> (raw) In-Reply-To: <20181210070044.27503-1-ruscur@russell.cc> __patch_instruction() is called in early boot, and uses __put_user_size(), which includes the locks and unlocks for KUAP, which could either be called too early, or in the Radix case, forced to use "early_" versions of functions just to safely handle this one case. __put_user_asm() does not do this, and thus is safe to use both in early boot, and later on since in this case it should only ever be touching kernel memory. __patch_instruction() was previously refactored to use __put_user_size() in order to be able to return -EFAULT, which would allow the kernel to patch instructions in userspace, which should never happen. This has the functional change of causing faults on userspace addresses if KUAP is turned on, which should never happen in practice. A future enhancement could be to double check the patch address is definitely allowed to be tampered with by the kernel. Signed-off-by: Russell Currey <ruscur@russell.cc> --- arch/powerpc/lib/code-patching.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c index 89502cbccb1b..15e8c6339960 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -26,9 +26,9 @@ static int __patch_instruction(unsigned int *exec_addr, unsigned int instr, unsigned int *patch_addr) { - int err; + int err = 0; - __put_user_size(instr, patch_addr, 4, err); + __put_user_asm(instr, patch_addr, err, "stw"); if (err) return err; -- 2.19.2
WARNING: multiple messages have this Message-ID (diff)
From: Russell Currey <ruscur@russell.cc> To: linuxppc-dev@lists.ozlabs.org Cc: mikey@neuling.org, mpe@ellerman.id.au, benh@kernel.crashing.org, npiggin@gmail.com, christophe.leroy@c-s.fr, kernel-hardening@lists.openwall.com, Russell Currey <ruscur@russell.cc> Subject: [PATCH v2 2/3] powerpc/lib: Refactor __patch_instruction() to use __put_user_asm() Date: Mon, 10 Dec 2018 18:00:43 +1100 [thread overview] Message-ID: <20181210070044.27503-3-ruscur@russell.cc> (raw) In-Reply-To: <20181210070044.27503-1-ruscur@russell.cc> __patch_instruction() is called in early boot, and uses __put_user_size(), which includes the locks and unlocks for KUAP, which could either be called too early, or in the Radix case, forced to use "early_" versions of functions just to safely handle this one case. __put_user_asm() does not do this, and thus is safe to use both in early boot, and later on since in this case it should only ever be touching kernel memory. __patch_instruction() was previously refactored to use __put_user_size() in order to be able to return -EFAULT, which would allow the kernel to patch instructions in userspace, which should never happen. This has the functional change of causing faults on userspace addresses if KUAP is turned on, which should never happen in practice. A future enhancement could be to double check the patch address is definitely allowed to be tampered with by the kernel. Signed-off-by: Russell Currey <ruscur@russell.cc> --- arch/powerpc/lib/code-patching.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c index 89502cbccb1b..15e8c6339960 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -26,9 +26,9 @@ static int __patch_instruction(unsigned int *exec_addr, unsigned int instr, unsigned int *patch_addr) { - int err; + int err = 0; - __put_user_size(instr, patch_addr, 4, err); + __put_user_asm(instr, patch_addr, err, "stw"); if (err) return err; -- 2.19.2
next prev parent reply other threads:[~2018-12-10 7:03 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-12-10 7:00 [PATCH v2 0/3] [PATCH v2 0/3] Kernel Userspace Protection for Radix MMU Russell Currey 2018-12-10 7:00 ` Russell Currey 2018-12-10 7:00 ` [PATCH v2 1/3] powerpc/mm/radix: Use KUEP API " Russell Currey 2018-12-10 7:00 ` Russell Currey 2018-12-10 7:00 ` Russell Currey [this message] 2018-12-10 7:00 ` [PATCH v2 2/3] powerpc/lib: Refactor __patch_instruction() to use __put_user_asm() Russell Currey 2018-12-17 7:09 ` Christophe Leroy 2018-12-17 7:09 ` Christophe Leroy 2019-01-25 11:45 ` Christophe Leroy 2019-01-25 11:45 ` Christophe Leroy 2019-02-20 11:57 ` Russell Currey 2019-02-20 11:57 ` Russell Currey 2018-12-10 7:00 ` [PATCH v2 3/3] powerpc/64s: Implement KUAP for Radix MMU Russell Currey 2018-12-10 7:00 ` Russell Currey
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