vfs/proc/kcore, x86/mm/kcore: Fix SMAP fault when dumping vsyscall user page (595dd46e) · Commits · 戴 / test

Commit: ("fs/proc/kcore.c: Add bounce buffer for ktext data") ... introduced a bounce buffer to work around CONFIG_HARDENED_USERCOPY=y. However, accessing the vsyscall user page will cause an SMAP fault. Replace memcpy() with copy_from_user() to fix this bug works, but adding a common way to handle this sort of user page may be useful for future. Currently, only vsyscall page requires KCORE_USER. Signed-off-by:

Jia Zhang <zhang.jia@linux.alibaba.com> Reviewed-by:

Jiri Olsa <jolsa@kernel.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: jolsa@redhat.com Link: http://lkml.kernel.org/r/1518446694-21124-2-git-send-email-zhang.jia@linux.alibaba.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

arch/x86/mm/init_64.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -1193,8 +1193,7 @@ void __init mem_init(void)
		register_page_bootmem_info();

		/* Register memory areas for /proc/kcore */
		kclist_add(&kcore_vsyscall, (void *)VSYSCALL_ADDR,
		PAGE_SIZE, KCORE_OTHER);
		kclist_add(&kcore_vsyscall, (void *)VSYSCALL_ADDR, PAGE_SIZE, KCORE_USER);

		mem_init_print_info(NULL);
		}

fs/proc/kcore.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -510,6 +510,10 @@ read_kcore(struct file file, char __user buffer, size_t buflen, loff_t *fpos)
		/* we have to zero-fill user buffer even if no read */
		if (copy_to_user(buffer, buf, tsz))
		return -EFAULT;
		} else if (m->type == KCORE_USER) {
		/* User page is handled prior to normal kernel page: */
		if (copy_to_user(buffer, (char *)start, tsz))
		return -EFAULT;
		} else {
		if (kern_addr_valid(start)) {
		/*

include/linux/kcore.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -10,6 +10,7 @@ enum kcore_type {
		KCORE_VMALLOC,
		KCORE_RAM,
		KCORE_VMEMMAP,
		KCORE_USER,
		KCORE_OTHER,
		};

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