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Btrfs: fix an integer overflow check 

This isn't super serious because you need CAP_ADMIN to run this code.

I added this integer overflow check last year but apparently I am
rubbish at writing integer overflow checks...  There are two issues.
First, access_ok() works on unsigned long type and not u64 so on 32 bit
systems the access_ok() could be checking a truncated size.  The other
issue is that we should be using a stricter limit so we don't overflow
the kzalloc() setting ctx->clone_roots later in the function after the
access_ok():

	alloc_size = sizeof(struct clone_root) * (arg->clone_sources_count + 1);
	sctx->clone_roots = kzalloc(alloc_size, GFP_KERNEL | __GFP_NOWARN);

Fixes: f5ecec3ce2 ("btrfs: send: silence an integer overflow warning")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ added comment ]
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Dan Carpenter 2017-03-17 23:51:20 +03:00 committed by David Sterba
parent ce0dcee626
commit 457ae7268b
1 changed files with 6 additions and 1 deletions
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7
fs/btrfs/send.c
View File

@ -6305,8 +6305,13 @@ long btrfs_ioctl_send(struct file *mnt_file, void __user *arg_)
goto out;
}
/*
* Check that we don't overflow at later allocations, we request
* clone_sources_count + 1 items, and compare to unsigned long inside
* access_ok.
*/
if (arg->clone_sources_count >
ULLONG_MAX / sizeof(*arg->clone_sources)) {
ULONG_MAX / sizeof(struct clone_root) - 1) {
ret = -EINVAL;
goto out;
}