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 4.14-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-4.14 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 08:20:38 AM CET 2020 From: Daniel Axtens <dja@xxxxxxxxxx> Date: Fri, 20 Nov 2020 10:52:42 +1100 Subject: powerpc: Fix __clear_user() with KUAP enabled To: stable@xxxxxxxxxxxxxxx Cc: dja@xxxxxxxxxx Message-ID: <20201119235244.373127-7-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/lib/string.S | 4 ++-- arch/powerpc/lib/string_64.S | 6 +++--- 3 files changed, 12 insertions(+), 7 deletions(-) --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -390,7 +390,7 @@ raw_copy_to_user(void __user *to, const return ret; } -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) { @@ -398,12 +398,17 @@ 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 strnlen_user(const char __user *str, long n); --- a/arch/powerpc/lib/string.S +++ b/arch/powerpc/lib/string.S @@ -88,7 +88,7 @@ _GLOBAL(memchr) EXPORT_SYMBOL(memchr) #ifdef CONFIG_PPC32 -_GLOBAL(__clear_user) +_GLOBAL(__arch_clear_user) addi r6,r3,-4 li r3,0 li r5,0 @@ -128,5 +128,5 @@ _GLOBAL(__clear_user) EX_TABLE(1b, 91b) EX_TABLE(8b, 92b) -EXPORT_SYMBOL(__clear_user) +EXPORT_SYMBOL(__arch_clear_user) #endif --- a/arch/powerpc/lib/string_64.S +++ b/arch/powerpc/lib/string_64.S @@ -29,7 +29,7 @@ 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. * @@ -70,7 +70,7 @@ 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 @@ -193,4 +193,4 @@ err1; dcbz 0,r3 cmpdi r4,32 blt .Lshort_clear b .Lmedium_clear -EXPORT_SYMBOL(__clear_user) +EXPORT_SYMBOL(__arch_clear_user) Patches currently in stable-queue which might be from dja@xxxxxxxxxx are queue-4.14/powerpc-add-a-framework-for-user-access-tracking.patch queue-4.14/powerpc-implement-user_access_begin-and-friends.patch queue-4.14/powerpc-uaccess-evaluate-macro-arguments-once-before-user-access-is-allowed.patch queue-4.14/powerpc-64s-flush-l1d-after-user-accesses.patch queue-4.14/powerpc-64s-move-some-exception-handlers-out-of-line.patch queue-4.14/powerpc-64s-flush-l1d-on-kernel-entry.patch queue-4.14/powerpc-fix-__clear_user-with-kuap-enabled.patch queue-4.14/powerpc-64s-define-maskable_relon_exception_pseries_ool.patch