This is a note to let you know that I've just added the patch titled powerpc: Fix __clear_user() with KUAP enabled to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: powerpc-fix-__clear_user-with-kuap-enabled.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Fri Nov 20 08:28:41 AM CET 2020 From: Daniel Axtens <dja@xxxxxxxxxx> Date: Fri, 20 Nov 2020 11:07:02 +1100 Subject: powerpc: Fix __clear_user() with KUAP enabled To: stable@xxxxxxxxxxxxxxx Cc: dja@xxxxxxxxxx Message-ID: <20201120000704.374811-7-dja@xxxxxxxxxx> From: Andrew Donnellan <ajd@xxxxxxxxxxxxx> commit 61e3acd8c693a14fc69b824cb5b08d02cb90a6e7 upstream. The KUAP implementation adds calls in clear_user() to enable and disable access to userspace memory. However, it doesn't add these to __clear_user(), which is used in the ptrace regset code. As there's only one direct user of __clear_user() (the regset code), and the time taken to set the AMR for KUAP purposes is going to dominate the cost of a quick access_ok(), there's not much point having a separate path. Rename __clear_user() to __arch_clear_user(), and make __clear_user() just call clear_user(). Reported-by: syzbot+f25ecf4b2982d8c7a640@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Reported-by: Daniel Axtens <dja@xxxxxxxxxx> Suggested-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Fixes: de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access Protection") Signed-off-by: Andrew Donnellan <ajd@xxxxxxxxxxxxx> [mpe: Use __arch_clear_user() for the asm version like arm64 & nds32] Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20191209132221.15328-1-ajd@xxxxxxxxxxxxx Signed-off-by: Daniel Axtens <dja@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/powerpc/include/asm/uaccess.h | 9 +++++++-- arch/powerpc/kernel/ppc_ksyms.c | 3 +++ arch/powerpc/lib/string.S | 2 +- arch/powerpc/lib/string_64.S | 4 ++-- 4 files changed, 13 insertions(+), 5 deletions(-) --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -471,7 +471,7 @@ static inline unsigned long __copy_to_us return __copy_to_user_inatomic(to, from, size); } -extern unsigned long __clear_user(void __user *addr, unsigned long size); +unsigned long __arch_clear_user(void __user *addr, unsigned long size); static inline unsigned long clear_user(void __user *addr, unsigned long size) { @@ -479,12 +479,17 @@ static inline unsigned long clear_user(v might_fault(); if (likely(access_ok(VERIFY_WRITE, addr, size))) { allow_write_to_user(addr, size); - ret = __clear_user(addr, size); + ret = __arch_clear_user(addr, size); prevent_write_to_user(addr, size); } return ret; } +static inline unsigned long __clear_user(void __user *addr, unsigned long size) +{ + return clear_user(addr, size); +} + extern long strncpy_from_user(char *dst, const char __user *src, long count); extern __must_check long strlen_user(const char __user *str); extern __must_check long strnlen_user(const char __user *str, long n); --- a/arch/powerpc/kernel/ppc_ksyms.c +++ b/arch/powerpc/kernel/ppc_ksyms.c @@ -5,6 +5,7 @@ #include <asm/switch_to.h> #include <asm/cacheflush.h> #include <asm/epapr_hcalls.h> +#include <asm/uaccess.h> EXPORT_SYMBOL(flush_dcache_range); EXPORT_SYMBOL(flush_icache_range); @@ -43,3 +44,5 @@ EXPORT_SYMBOL(epapr_hypercall_start); #endif EXPORT_SYMBOL(current_stack_pointer); + +EXPORT_SYMBOL(__arch_clear_user); --- a/arch/powerpc/lib/string.S +++ b/arch/powerpc/lib/string.S @@ -122,7 +122,7 @@ _GLOBAL(memchr) blr #ifdef CONFIG_PPC32 -_GLOBAL(__clear_user) +_GLOBAL(__arch_clear_user) addi r6,r3,-4 li r3,0 li r5,0 --- a/arch/powerpc/lib/string_64.S +++ b/arch/powerpc/lib/string_64.S @@ -27,7 +27,7 @@ PPC64_CACHES: .section ".text" /** - * __clear_user: - Zero a block of memory in user space, with less checking. + * __arch_clear_user: - Zero a block of memory in user space, with less checking. * @to: Destination address, in user space. * @n: Number of bytes to zero. * @@ -77,7 +77,7 @@ err3; stb r0,0(r3) mr r3,r4 blr -_GLOBAL_TOC(__clear_user) +_GLOBAL_TOC(__arch_clear_user) cmpdi r4,32 neg r6,r3 li r0,0 Patches currently in stable-queue which might be from dja@xxxxxxxxxx are queue-4.4/powerpc-add-a-framework-for-user-access-tracking.patch queue-4.4/powerpc-implement-user_access_begin-and-friends.patch queue-4.4/powerpc-uaccess-evaluate-macro-arguments-once-before-user-access-is-allowed.patch queue-4.4/powerpc-64s-flush-l1d-after-user-accesses.patch queue-4.4/powerpc-64s-move-some-exception-handlers-out-of-line.patch queue-4.4/powerpc-64s-flush-l1d-on-kernel-entry.patch queue-4.4/powerpc-fix-__clear_user-with-kuap-enabled.patch queue-4.4/powerpc-64s-define-maskable_relon_exception_pseries_ool.patch