From: Eric Sandeen sandeen@redhat.com
commit cc3a7bfe62b947b423fcb2cfe89fcba92bf48fa3 upstream.
Today, put_compat_statfs64() disallows nearly any field value over 2^32 if f_bsize is only 32 bits, but that makes no sense. compat_statfs64 is there for the explicit purpose of providing 64-bit fields for f_files, f_ffree, etc. And f_bsize is always only 32 bits.
As a result, 32-bit userspace gets -EOVERFLOW for i.e. large file counts even with -D_FILE_OFFSET_BITS=64 set.
In reality, only f_bsize and f_frsize can legitimately overflow (fields like f_type and f_namelen should never be large), so test only those fields.
This bug was discussed at length some time ago, and this is the proposal Al suggested at https://lkml.org/lkml/2018/8/6/640. It seemed to get dropped amid the discussion of other related changes, but this part seems obviously correct on its own, so I've picked it up and sent it, for expediency.
Fixes: 64d2ab32efe3 ("vfs: fix put_compat_statfs64() does not handle errors") Signed-off-by: Eric Sandeen sandeen@redhat.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/statfs.c | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-)
--- a/fs/statfs.c +++ b/fs/statfs.c @@ -304,19 +304,10 @@ COMPAT_SYSCALL_DEFINE2(fstatfs, unsigned static int put_compat_statfs64(struct compat_statfs64 __user *ubuf, struct kstatfs *kbuf) { struct compat_statfs64 buf; - if (sizeof(ubuf->f_bsize) == 4) { - if ((kbuf->f_type | kbuf->f_bsize | kbuf->f_namelen | - kbuf->f_frsize | kbuf->f_flags) & 0xffffffff00000000ULL) - return -EOVERFLOW; - /* f_files and f_ffree may be -1; it's okay - * to stuff that into 32 bits */ - if (kbuf->f_files != 0xffffffffffffffffULL - && (kbuf->f_files & 0xffffffff00000000ULL)) - return -EOVERFLOW; - if (kbuf->f_ffree != 0xffffffffffffffffULL - && (kbuf->f_ffree & 0xffffffff00000000ULL)) - return -EOVERFLOW; - } + + if ((kbuf->f_bsize | kbuf->f_frsize) & 0xffffffff00000000ULL) + return -EOVERFLOW; + memset(&buf, 0, sizeof(struct compat_statfs64)); buf.f_type = kbuf->f_type; buf.f_bsize = kbuf->f_bsize;