linux-kernel - [PATCH 1/2] fs/proc: kcore: use kcore_list type to check for vmalloc/module address

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Date:   Thu,  8 Jun 2017 19:41:38 +0000
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org, jolsa@...nel.org,
        mingo@...nel.org, akpm@...ux-foundation.org, zhongjiang@...wei.com,
        labbott@...oraproject.org, mark.rutland@....com,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [PATCH 1/2] fs/proc: kcore: use kcore_list type to check for vmalloc/module address

Instead of passing each start address into is_vmalloc_or_module_addr()
to decide whether it falls into either the VMALLOC or the MODULES region,
we can simply check the type field of the current kcore_list entry, since
it will be set to KCORE_VMALLOC based on exactly the same conditions.

As a bonus, when reading the KCORE_TEXT region on architectures that have
one, this will avoid using vread() on the region if it happens to intersect
with a KCORE_VMALLOC region. This is due the fact that the KCORE_TEXT
region is the first one to be added to the kcore region list.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
 fs/proc/kcore.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 4ee55274f155..45629f4b5402 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -504,7 +504,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 		if (&m->list == &kclist_head) {
 			if (clear_user(buffer, tsz))
 				return -EFAULT;
-		} else if (is_vmalloc_or_module_addr((void *)start)) {
+		} else if (m->type == KCORE_VMALLOC) {
 			vread(buf, (char *)start, tsz);
 			/* we have to zero-fill user buffer even if no read */
 			if (copy_to_user(buffer, buf, tsz))
-- 
2.9.3