[PATCH] asm-generic: uaccess: avoid name conflicts for strncpy and str(n)len

[PATCH] asm-generic: uaccess: avoid name conflicts for strncpy and str(n)len

[Joel Porquet]

asm-generic/uaccess.h defines 'strncpy_from_user', 'strnlen_user' and
'strlen_user' as static inline functions. It makes it impossible for an
arch to include asm-generic/uaccess.h and benefits from its content, in
addition to defining GENERIC_STRNCPY_FROM_USER and GENERIC_STRNLEN_USER.

Both configuration tokens respectively enable lib/strncpy_from_user.c
and lib/strnlen_user.c which redefine the same symbols, causing
redefinition errors at compilation.

This patch modifies asm-generic/uaccess.h so that strncpy_from_user is
not defined when GENERIC_STRNCPY_FROM_USER is, and strnlen_user and
strlen_user are not defined when GENERIC_STRNLEN_USER is, thus avoiding
any name conflict.

At the moment, numerous archs, which make use of
GENERIC_STRNCPY_FROM_USER and GENERIC_STRNLEN_USER, are forced to
rewrite an entire asm/uaccess.h header because of this issue.

To the best of my knowledge, the following list of archs could benefit
from this patch: x86, sh, openrisc, powerpc, arm64, arm, alpha, parisc,
sparc, m68k.

Signed-off-by: Joel Porquet <joel@porquet.org>
---
 include/asm-generic/uaccess.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
index 72d8803..4198d84 100644
--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -272,6 +272,7 @@ static inline long copy_to_user(void __user *to,
 		return n;
 }
 
+#ifndef CONFIG_GENERIC_STRNCPY_FROM_USER
 /*
  * Copy a null terminated string from userspace.
  */
@@ -294,7 +295,9 @@ strncpy_from_user(char *dst, const char __user *src, long count)
 		return -EFAULT;
 	return __strncpy_from_user(dst, src, count);
 }
+#endif
 
+#ifndef CONFIG_GENERIC_STRNLEN_USER
 /*
  * Return the size of a string (including the ending 0)
  *
@@ -320,6 +323,7 @@ static inline long strlen_user(const char __user *src)
 {
 	return strnlen_user(src, 32767);
 }
+#endif
 
 /*
  * Zero Userspace
-- 
1.9.3

Re: [PATCH] asm-generic: uaccess: avoid name conflicts for strncpy and str(n)len

[Arnd Bergmann]

On Wednesday 28 May 2014 17:21:51 Joel Porquet wrote:
> asm-generic/uaccess.h defines 'strncpy_from_user', 'strnlen_user' and
> 'strlen_user' as static inline functions. It makes it impossible for an
> arch to include asm-generic/uaccess.h and benefits from its content, in
> addition to defining GENERIC_STRNCPY_FROM_USER and GENERIC_STRNLEN_USER.
> 
> Both configuration tokens respectively enable lib/strncpy_from_user.c
> and lib/strnlen_user.c which redefine the same symbols, causing
> redefinition errors at compilation.
> 
> This patch modifies asm-generic/uaccess.h so that strncpy_from_user is
> not defined when GENERIC_STRNCPY_FROM_USER is, and strnlen_user and
> strlen_user are not defined when GENERIC_STRNLEN_USER is, thus avoiding
> any name conflict.
> 
> At the moment, numerous archs, which make use of
> GENERIC_STRNCPY_FROM_USER and GENERIC_STRNLEN_USER, are forced to
> rewrite an entire asm/uaccess.h header because of this issue.
> 
> To the best of my knowledge, the following list of archs could benefit
> from this patch: x86, sh, openrisc, powerpc, arm64, arm, alpha, parisc,
> sparc, m68k.
> 
> Signed-off-by: Joel Porquet <joel@porquet.org>
> 

Acked-by: Arnd Bergmann <arnd@arndb.de>

It makes sense to do this for any architecture that want's to use
this file, so feel free to add your patch the tree of whatever architecture
you want to convert.

Note however that asm/uaccess.h can't be implemented correctly in
generic code: you always need inline assembly to add the correct fixup
section magic.

	Arnd