[PATCH 13/30] x86, kaiser: map dynamically-allocated LDTs
From: Dave Hansen <dave.hansen@linux.intel.com>
Date: 2017-11-10 19:31:49
Also in:
lkml
From: Dave Hansen <dave.hansen@linux.intel.com> Normally, a process has a NULL mm->context.ldt. But, there is a syscall for a process to set a new one. If a process does that, the LDT be mapped into the user page tables, just like the default copy. The original KAISER patch missed this case. Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Moritz Lipp <redacted> Cc: Daniel Gruss <redacted> Cc: Michael Schwarz <redacted> Cc: Richard Fellner <redacted> Cc: Andy Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Kees Cook <redacted> Cc: Hugh Dickins <hughd@google.com> Cc: x86@kernel.org --- b/arch/x86/kernel/ldt.c | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-) diff -puN arch/x86/kernel/ldt.c~kaiser-user-map-new-ldts arch/x86/kernel/ldt.c
--- a/arch/x86/kernel/ldt.c~kaiser-user-map-new-ldts 2017-11-10 11:22:12.127244942 -0800
+++ b/arch/x86/kernel/ldt.c 2017-11-10 11:22:12.131244942 -0800@@ -10,6 +10,7 @@ #include <linux/gfp.h> #include <linux/sched.h> #include <linux/string.h> +#include <linux/kaiser.h> #include <linux/mm.h> #include <linux/smp.h> #include <linux/syscalls.h>
@@ -56,11 +57,21 @@ static void flush_ldt(void *__mm) refresh_ldt_segments(); } +static void __free_ldt_struct(struct ldt_struct *ldt) +{ + if (ldt->nr_entries * LDT_ENTRY_SIZE > PAGE_SIZE) + vfree_atomic(ldt->entries); + else + free_page((unsigned long)ldt->entries); + kfree(ldt); +} + /* The caller must call finalize_ldt_struct on the result. LDT starts zeroed. */ static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries) { struct ldt_struct *new_ldt; unsigned int alloc_size; + int ret; if (num_entries > LDT_ENTRIES) return NULL;
@@ -88,6 +99,12 @@ static struct ldt_struct *alloc_ldt_stru return NULL; } + ret = kaiser_add_mapping((unsigned long)new_ldt->entries, alloc_size, + __PAGE_KERNEL | _PAGE_GLOBAL); + if (ret) { + __free_ldt_struct(new_ldt); + return NULL; + } new_ldt->nr_entries = num_entries; return new_ldt; }
@@ -114,12 +131,10 @@ static void free_ldt_struct(struct ldt_s if (likely(!ldt)) return; + kaiser_remove_mapping((unsigned long)ldt->entries, + ldt->nr_entries * LDT_ENTRY_SIZE); paravirt_free_ldt(ldt->entries, ldt->nr_entries); - if (ldt->nr_entries * LDT_ENTRY_SIZE > PAGE_SIZE) - vfree_atomic(ldt->entries); - else - free_page((unsigned long)ldt->entries); - kfree(ldt); + __free_ldt_struct(ldt); } /*
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