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lkdtm: Test copy_to_user() on bad kernel pointer under KERNEL_DS
Test whether the kernel WARN()s when, under KERNEL_DS, a bad kernel pointer is used as "userspace" pointer. Should normally be used in "DIRECT" mode. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Kees Cook <keescook@chromium.org> Acked-by: Kees Cook <keescook@chromium.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: kernel-hardening@lists.openwall.com Cc: dvyukov@google.com Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Cc: Borislav Petkov <bp@alien8.de> Link: https://lkml.kernel.org/r/20180828201421.157735-8-jannh@google.com
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3 changed files with 15 additions and 0 deletions
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@ -183,6 +183,7 @@ static const struct crashtype crashtypes[] = {
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CRASHTYPE(USERCOPY_STACK_FRAME_FROM),
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CRASHTYPE(USERCOPY_STACK_BEYOND),
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CRASHTYPE(USERCOPY_KERNEL),
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CRASHTYPE(USERCOPY_KERNEL_DS),
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};
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@ -82,5 +82,6 @@ void lkdtm_USERCOPY_STACK_FRAME_TO(void);
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void lkdtm_USERCOPY_STACK_FRAME_FROM(void);
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void lkdtm_USERCOPY_STACK_BEYOND(void);
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void lkdtm_USERCOPY_KERNEL(void);
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void lkdtm_USERCOPY_KERNEL_DS(void);
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#endif
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@ -322,6 +322,19 @@ void lkdtm_USERCOPY_KERNEL(void)
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vm_munmap(user_addr, PAGE_SIZE);
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}
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void lkdtm_USERCOPY_KERNEL_DS(void)
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{
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char __user *user_ptr = (char __user *)ERR_PTR(-EINVAL);
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mm_segment_t old_fs = get_fs();
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char buf[10] = {0};
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pr_info("attempting copy_to_user on unmapped kernel address\n");
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set_fs(KERNEL_DS);
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if (copy_to_user(user_ptr, buf, sizeof(buf)))
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pr_info("copy_to_user un unmapped kernel address failed\n");
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set_fs(old_fs);
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}
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void __init lkdtm_usercopy_init(void)
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{
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/* Prepare cache that lacks SLAB_USERCOPY flag. */
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