This is a note to let you know that I've just added the patch titled
wifi: wext-core: Fix -Wstringop-overflow warning in ioctl_standard_iw_point()
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
wifi-wext-core-fix-wstringop-overflow-warning-in-ioc.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit eec6c0631c177e946a67d88280585b6f80934407
Author: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Date: Thu Jun 15 12:04:07 2023 -0600
wifi: wext-core: Fix -Wstringop-overflow warning in ioctl_standard_iw_point()
[ Upstream commit 71e7552c90db2a2767f5c17c7ec72296b0d92061 ]
-Wstringop-overflow is legitimately warning us about extra_size
pontentially being zero at some point, hence potenially ending
up _allocating_ zero bytes of memory for extra pointer and then
trying to access such object in a call to copy_from_user().
Fix this by adding a sanity check to ensure we never end up
trying to allocate zero bytes of data for extra pointer, before
continue executing the rest of the code in the function.
Address the following -Wstringop-overflow warning seen when built
m68k architecture with allyesconfig configuration:
from net/wireless/wext-core.c:11:
In function '_copy_from_user',
inlined from 'copy_from_user' at include/linux/uaccess.h:183:7,
inlined from 'ioctl_standard_iw_point' at net/wireless/wext-core.c:825:7:
arch/m68k/include/asm/string.h:48:25: warning: '__builtin_memset' writing 1 or more bytes into a region of size 0 overflows the destination [-Wstringop-overflow=]
48 | #define memset(d, c, n) __builtin_memset(d, c, n)
| ^~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/uaccess.h:153:17: note: in expansion of macro 'memset'
153 | memset(to + (n - res), 0, res);
| ^~~~~~
In function 'kmalloc',
inlined from 'kzalloc' at include/linux/slab.h:694:9,
inlined from 'ioctl_standard_iw_point' at net/wireless/wext-core.c:819:10:
include/linux/slab.h:577:16: note: at offset 1 into destination object of size 0 allocated by '__kmalloc'
577 | return __kmalloc(size, flags);
| ^~~~~~~~~~~~~~~~~~~~~~
This help with the ongoing efforts to globally enable
-Wstringop-overflow.
Link: https://github.com/KSPP/linux/issues/315
Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/ZItSlzvIpjdjNfd8@work
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/wireless/wext-core.c b/net/wireless/wext-core.c
index 76a80a41615be..a57f54bc0e1a7 100644
--- a/net/wireless/wext-core.c
+++ b/net/wireless/wext-core.c
@@ -796,6 +796,12 @@ static int ioctl_standard_iw_point(struct iw_point *iwp, unsigned int cmd,
}
}
+ /* Sanity-check to ensure we never end up _allocating_ zero
+ * bytes of data for extra.
+ */
+ if (extra_size <= 0)
+ return -EFAULT;
+
/* kzalloc() ensures NULL-termination for essid_compat. */
extra = kzalloc(extra_size, GFP_KERNEL);
if (!extra)
