+ usercopy-do-not-fail-on-memory-from-former-init-sections.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: usercopy: do not fail on memory from former init sections
has been added to the -mm tree.  Its filename is
     usercopy-do-not-fail-on-memory-from-former-init-sections.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/usercopy-do-not-fail-on-memory-from-former-init-sections.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/usercopy-do-not-fail-on-memory-from-former-init-sections.patch

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------------------------------------------------------
From: Helge Deller <deller@gmx.de>
Subject: usercopy: do not fail on memory from former init sections

On some platforms the memory area between the _stext and the _etext
symbols includes the init sections (parisc and csky).  If the init
sections are freed after bootup, the kernel may reuse this memory.

In one test the usercopy checks if the given address is inside the .text
section (from _stext to _etext), and it wrongly fails on the mentioned
platforms if the memory is from the former init section.

Fix this failure by first checking against the init sections before
checking against the _stext/_etext section.

Link: https://lkml.kernel.org/r/YdeHDDAP+TY5wNeT@ls3530
Fixes: 98400ad75e95 ("parisc: Fix backtrace to always include init funtion names")
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/usercopy.c |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

--- a/mm/usercopy.c~usercopy-do-not-fail-on-memory-from-former-init-sections
+++ a/mm/usercopy.c
@@ -113,6 +113,15 @@ static bool overlaps(const unsigned long
 	return true;
 }
 
+static bool inside_init_area(const unsigned long ptr, unsigned long n,
+		char *start, char *end)
+{
+	unsigned long initlow = (unsigned long) start;
+	unsigned long inithigh = (unsigned long) end;
+
+	return (ptr >= initlow && (ptr + n) < inithigh);
+}
+
 /* Is this address range in the kernel text area? */
 static inline void check_kernel_text_object(const unsigned long ptr,
 					    unsigned long n, bool to_user)
@@ -121,6 +130,12 @@ static inline void check_kernel_text_obj
 	unsigned long texthigh = (unsigned long)_etext;
 	unsigned long textlow_linear, texthigh_linear;
 
+	/* Ok if inside the former init sections */
+	if (inside_init_area(ptr, n, __init_begin, __init_end))
+		return;
+	if (inside_init_area(ptr, n, _sinittext, _einittext))
+		return;
+
 	if (overlaps(ptr, n, textlow, texthigh))
 		usercopy_abort("kernel text", NULL, to_user, ptr - textlow, n);
 
_

Patches currently in -mm which might be from deller@gmx.de are

usercopy-do-not-fail-on-memory-from-former-init-sections.patch