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x86/umip: Factor out instruction fetch

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Factor out the code to fetch the instruction from user-space to a helper
function.

No functional changes.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-9-joro@8bytes.org
This commit is contained in:
Joerg Roedel 2020-09-07 15:15:09 +02:00 committed by Borislav Petkov
parent 05a2ae7c03
commit 172b75e56b
3 changed files with 46 additions and 20 deletions
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2
arch/x86/include/asm/insn-eval.h
View File

@ -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 */

26
arch/x86/kernel/umip.c
View File

@ -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;

38
arch/x86/lib/insn-eval.c
View File

@ -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;
}