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free_blocks(): Fix reports from 2016 PVS Studio FreeBSD report 

In 2016, the authors of PVS Studio ran it on the FreeBSD kernel, which
identified a number of bugs / cleanup opportunities in the FreeBSD ZFS kernel
code. A few of them persist to the present day:

https://reviews.freebsd.org/D5245

Note that the scan was done against
freebsd/freebsd-src@46763fd4ca.

In particular, we have the following in free_blocks():

\sys\cddl\contrib\opensolaris\uts\common\fs\zfs\dnode_sync.c (174): error V547: Expression '__left >= __right' is always true. Unsigned type value is always >= 0.
\sys\cddl\contrib\opensolaris\uts\common\fs\zfs\dnode_sync.c (171): error V634: The priority of the '*' operation is higher than that of the '<<' operation. It's possible that parentheses should be used in the expression.
\sys\cddl\contrib\opensolaris\uts\common\fs\zfs\dnode_sync.c (175): error V547: Expression '__left >= __right' is always true. Unsigned type value is always >= 0.

A couple of assertions accidentally typecast the arguments they check to
unsigned in such a way that the result is always true. Also, parentheses
are missing around `1<<epbs` in `(db->db_blkid * 1<<epbs)`. This works
out to be okay due to multiplication not caring what order of operations
we use, but it is better to fix it to be `(db->db_blkid << epbs)`.

A few of the function local variables probably never should have been
32-bit in the first place, so we make them 64-bit. We also replace the
existing assertions with additional assertions to ensure that 64-bit
unsigned arithmetic is safe.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes #14407
This commit is contained in:
Richard Yao 2023-01-23 16:12:37 -05:00 committed by GitHub
parent 71974946be
commit f091db9248
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1 changed files with 17 additions and 10 deletions
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27
module/zfs/dnode_sync.c
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@ -175,19 +175,21 @@ free_blocks(dnode_t *dn, blkptr_t *bp, int num, dmu_tx_t *tx)
static void
free_verify(dmu_buf_impl_t *db, uint64_t start, uint64_t end, dmu_tx_t *tx)
{
int off, num;
int i, err, epbs;
uint64_t off, num, i, j;
unsigned int epbs;
int err;
uint64_t txg = tx->tx_txg;
dnode_t *dn;
DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
epbs = dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT;
off = start - (db->db_blkid * 1<<epbs);
off = start - (db->db_blkid << epbs);
num = end - start + 1;
ASSERT3U(off, >=, 0);
ASSERT3U(num, >=, 0);
ASSERT3U(dn->dn_phys->dn_indblkshift, >=, SPA_BLKPTRSHIFT);
ASSERT3U(end + 1, >=, start);
ASSERT3U(start, >=, (db->db_blkid << epbs));
ASSERT3U(db->db_level, >, 0);
ASSERT3U(db->db.db_size, ==, 1 << dn->dn_phys->dn_indblkshift);
ASSERT3U(off+num, <=, db->db.db_size >> SPA_BLKPTRSHIFT);
@ -197,7 +199,6 @@ free_verify(dmu_buf_impl_t *db, uint64_t start, uint64_t end, dmu_tx_t *tx)
uint64_t *buf;
dmu_buf_impl_t *child;
dbuf_dirty_record_t *dr;
int j;
ASSERT(db->db_level == 1);
@ -217,8 +218,11 @@ free_verify(dmu_buf_impl_t *db, uint64_t start, uint64_t end, dmu_tx_t *tx)
for (j = 0; j < child->db.db_size >> 3; j++) {
if (buf[j] != 0) {
panic("freed data not zero: "
"child=%p i=%d off=%d num=%d\n",
(void *)child, i, off, num);
"child=%p i=%llu off=%llu "
"num=%llu\n",
(void *)child, (u_longlong_t)i,
(u_longlong_t)off,
(u_longlong_t)num);
}
}
}
@ -234,8 +238,11 @@ free_verify(dmu_buf_impl_t *db, uint64_t start, uint64_t end, dmu_tx_t *tx)
for (j = 0; j < child->db.db_size >> 3; j++) {
if (buf[j] != 0) {
panic("freed data not zero: "
"child=%p i=%d off=%d num=%d\n",
(void *)child, i, off, num);
"child=%p i=%llu off=%llu "
"num=%llu\n",
(void *)child, (u_longlong_t)i,
(u_longlong_t)off,
(u_longlong_t)num);
}
}
}