The following commit has been merged into the x86/seves branch of tip: Commit-ID: 172b75e56b08846e6fb07a88e5685ce4e24f4620 Gitweb: https://git.kernel.org/tip/172b75e56b08846e6fb07a88e5685ce4e24f4620 Author: Joerg Roedel <jroedel@xxxxxxx> AuthorDate: Mon, 07 Sep 2020 15:15:09 +02:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Mon, 07 Sep 2020 19:45:24 +02:00 x86/umip: Factor out instruction fetch Factor out the code to fetch the instruction from user-space to a helper function. No functional changes. Signed-off-by: Joerg Roedel <jroedel@xxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Link: https://lkml.kernel.org/r/20200907131613.12703-9-joro@xxxxxxxxxx --- arch/x86/include/asm/insn-eval.h | 2 ++- arch/x86/kernel/umip.c | 26 ++++----------------- arch/x86/lib/insn-eval.c | 38 +++++++++++++++++++++++++++++++- 3 files changed, 46 insertions(+), 20 deletions(-) diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h index 2b6ccf2..b8b9ef1 100644 --- a/arch/x86/include/asm/insn-eval.h +++ b/arch/x86/include/asm/insn-eval.h @@ -19,5 +19,7 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs); int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs); unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx); int insn_get_code_seg_params(struct pt_regs *regs); +int insn_fetch_from_user(struct pt_regs *regs, + unsigned char buf[MAX_INSN_SIZE]); #endif /* _ASM_X86_INSN_EVAL_H */ diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c index 2c304fd..ad135be 100644 --- a/arch/x86/kernel/umip.c +++ b/arch/x86/kernel/umip.c @@ -335,11 +335,11 @@ static void force_sig_info_umip_fault(void __user *addr, struct pt_regs *regs) */ bool fixup_umip_exception(struct pt_regs *regs) { - int not_copied, nr_copied, reg_offset, dummy_data_size, umip_inst; - unsigned long seg_base = 0, *reg_addr; + int nr_copied, reg_offset, dummy_data_size, umip_inst; /* 10 bytes is the maximum size of the result of UMIP instructions */ unsigned char dummy_data[10] = { 0 }; unsigned char buf[MAX_INSN_SIZE]; + unsigned long *reg_addr; void __user *uaddr; struct insn insn; int seg_defs; @@ -347,26 +347,12 @@ bool fixup_umip_exception(struct pt_regs *regs) if (!regs) return false; - /* - * If not in user-space long mode, a custom code segment could be in - * use. This is true in protected mode (if the process defined a local - * descriptor table), or virtual-8086 mode. In most of the cases - * seg_base will be zero as in USER_CS. - */ - if (!user_64bit_mode(regs)) - seg_base = insn_get_seg_base(regs, INAT_SEG_REG_CS); - - if (seg_base == -1L) - return false; - - not_copied = copy_from_user(buf, (void __user *)(seg_base + regs->ip), - sizeof(buf)); - nr_copied = sizeof(buf) - not_copied; + nr_copied = insn_fetch_from_user(regs, buf); /* - * The copy_from_user above could have failed if user code is protected - * by a memory protection key. Give up on emulation in such a case. - * Should we issue a page fault? + * The insn_fetch_from_user above could have failed if user code + * is protected by a memory protection key. Give up on emulation + * in such a case. Should we issue a page fault? */ if (!nr_copied) return false; diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index 5e69603..947b7f1 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -1367,3 +1367,41 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) return (void __user *)-1L; } } + +/** + * insn_fetch_from_user() - Copy instruction bytes from user-space memory + * @regs: Structure with register values as seen when entering kernel mode + * @buf: Array to store the fetched instruction + * + * Gets the linear address of the instruction and copies the instruction bytes + * to the buf. + * + * Returns: + * + * Number of instruction bytes copied. + * + * 0 if nothing was copied. + */ +int insn_fetch_from_user(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE]) +{ + unsigned long seg_base = 0; + int not_copied; + + /* + * If not in user-space long mode, a custom code segment could be in + * use. This is true in protected mode (if the process defined a local + * descriptor table), or virtual-8086 mode. In most of the cases + * seg_base will be zero as in USER_CS. + */ + if (!user_64bit_mode(regs)) { + seg_base = insn_get_seg_base(regs, INAT_SEG_REG_CS); + if (seg_base == -1L) + return 0; + } + + + not_copied = copy_from_user(buf, (void __user *)(seg_base + regs->ip), + MAX_INSN_SIZE); + + return MAX_INSN_SIZE - not_copied; +}
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