From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 983222F24 for ; Wed, 12 Apr 2023 08:50:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1AA0BC433EF; Wed, 12 Apr 2023 08:50:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1681289423; bh=C3LSIZRJHufdaX7iBUhVu2WMe8ZJJeCpKaH9KVH70WI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EH9ihBEiZJxrNts7gsPXXrKft/tMQ8FmXLvR8lPykxNJ3KnaymtMWb2TsxadhEYQa qKdkR3q/BJp43guPJv/HChEIaEmYMX2IzIVMiHy1SuiC+59s940xZiB3eVZkMjoiuQ cwJ3SJypTYn9mKlojL31Bsr1CL0bZr1N17M7yoZo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, kernel test robot , Dan Carpenter , Ard Biesheuvel , Catalin Marinas , Sasha Levin Subject: [PATCH 6.2 053/173] arm64: compat: Work around uninitialized variable warning Date: Wed, 12 Apr 2023 10:32:59 +0200 Message-Id: <20230412082840.266560427@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230412082838.125271466@linuxfoundation.org> References: <20230412082838.125271466@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Ard Biesheuvel [ Upstream commit 32d85999680601d01b2a36713c9ffd7397c8688b ] Dan reports that smatch complains about a potential uninitialized variable being used in the compat alignment fixup code. The logic is not wrong per se, but we do end up using an uninitialized variable if reading the instruction that triggered the alignment fault from user space faults, even if the fault ensures that the uninitialized value doesn't propagate any further. Given that we just give up and return 1 if any fault occurs when reading the instruction, let's get rid of the 'success handling' pattern that captures the fault in a variable and aborts later, and instead, just return 1 immediately if any of the get_user() calls result in an exception. Fixes: 3fc24ef32d3b ("arm64: compat: Implement misalignment fixups for multiword loads") Reported-by: kernel test robot Reported-by: Dan Carpenter Link: https://lore.kernel.org/r/202304021214.gekJ8yRc-lkp@intel.com/ Signed-off-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20230404103625.2386382-1-ardb@kernel.org Signed-off-by: Catalin Marinas Signed-off-by: Sasha Levin --- arch/arm64/kernel/compat_alignment.c | 32 ++++++++++++---------------- 1 file changed, 14 insertions(+), 18 deletions(-) diff --git a/arch/arm64/kernel/compat_alignment.c b/arch/arm64/kernel/compat_alignment.c index 5edec2f49ec98..deff21bfa6800 100644 --- a/arch/arm64/kernel/compat_alignment.c +++ b/arch/arm64/kernel/compat_alignment.c @@ -314,36 +314,32 @@ int do_compat_alignment_fixup(unsigned long addr, struct pt_regs *regs) int (*handler)(unsigned long addr, u32 instr, struct pt_regs *regs); unsigned int type; u32 instr = 0; - u16 tinstr = 0; int isize = 4; int thumb2_32b = 0; - int fault; instrptr = instruction_pointer(regs); if (compat_thumb_mode(regs)) { __le16 __user *ptr = (__le16 __user *)(instrptr & ~1); + u16 tinstr, tinst2; - fault = alignment_get_thumb(regs, ptr, &tinstr); - if (!fault) { - if (IS_T32(tinstr)) { - /* Thumb-2 32-bit */ - u16 tinst2; - fault = alignment_get_thumb(regs, ptr + 1, &tinst2); - instr = ((u32)tinstr << 16) | tinst2; - thumb2_32b = 1; - } else { - isize = 2; - instr = thumb2arm(tinstr); - } + if (alignment_get_thumb(regs, ptr, &tinstr)) + return 1; + + if (IS_T32(tinstr)) { /* Thumb-2 32-bit */ + if (alignment_get_thumb(regs, ptr + 1, &tinst2)) + return 1; + instr = ((u32)tinstr << 16) | tinst2; + thumb2_32b = 1; + } else { + isize = 2; + instr = thumb2arm(tinstr); } } else { - fault = alignment_get_arm(regs, (__le32 __user *)instrptr, &instr); + if (alignment_get_arm(regs, (__le32 __user *)instrptr, &instr)) + return 1; } - if (fault) - return 1; - switch (CODING_BITS(instr)) { case 0x00000000: /* 3.13.4 load/store instruction extensions */ if (LDSTHD_I_BIT(instr)) -- 2.39.2