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x86/mtrr: Don't copy uninitialized gentry fields back to userspace

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Currently the copy_to_user of data in the gentry struct is copying
uninitiaized data in field _pad from the stack to userspace.

Fix this by explicitly memset'ing gentry to zero, this also will zero any
compiler added padding fields that may be in struct (currently there are
none).

Detected by CoverityScan, CID#200783 ("Uninitialized scalar variable")

Fixes: b263b31e8ad6 ("x86, mtrr: Use explicit sizing and padding for the 64-bit ioctls")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
Cc: security@kernel.org
Link: https://lkml.kernel.org/r/20181218172956.1440-1-colin.king@canonical.com
This commit is contained in:
Colin Ian King 2018-12-18 17:29:56 +00:00 committed by Thomas Gleixner
parent 87ab4689ca
commit 32043fa065
1 changed files with 2 additions and 0 deletions
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arch/x86/kernel/cpu/mtrr/if.c
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@ -165,6 +165,8 @@ mtrr_ioctl(struct file *file, unsigned int cmd, unsigned long __arg)
struct mtrr_gentry gentry;
void __user *arg = (void __user *) __arg;
memset(&gentry, 0, sizeof(gentry));
switch (cmd) {
case MTRRIOC_ADD_ENTRY:
case MTRRIOC_SET_ENTRY: