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From: David Malcolm <dmalcolm@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-1768] analyzer: update "tainted" state of RHS in comparisons [PR106373] Date: Wed, 20 Jul 2022 21:28:13 +0000 (GMT) [thread overview] Message-ID: <20220720212813.B12133858C83@sourceware.org> (raw) https://gcc.gnu.org/g:5e830693dd335621940368b6d39b23afc2c98545 commit r13-1768-g5e830693dd335621940368b6d39b23afc2c98545 Author: David Malcolm <dmalcolm@redhat.com> Date: Wed Jul 20 17:25:35 2022 -0400 analyzer: update "tainted" state of RHS in comparisons [PR106373] Doing so fixes various false positives from -Wanalyzer-tainted-array-index at -O1 and above (e.g. seen on the Linux kernel) gcc/analyzer/ChangeLog: PR analyzer/106373 * sm-taint.cc (taint_state_machine::on_condition): Potentially update the state of the RHS as well as the LHS. gcc/testsuite/ChangeLog: PR analyzer/106373 * gcc.dg/analyzer/torture/taint-read-index-3.c: New test. Signed-off-by: David Malcolm <dmalcolm@redhat.com> Diff: --- gcc/analyzer/sm-taint.cc | 18 ++++++-- .../gcc.dg/analyzer/torture/taint-read-index-3.c | 52 ++++++++++++++++++++++ 2 files changed, 67 insertions(+), 3 deletions(-) diff --git a/gcc/analyzer/sm-taint.cc b/gcc/analyzer/sm-taint.cc index 9cb78886c9f..0486c01aaca 100644 --- a/gcc/analyzer/sm-taint.cc +++ b/gcc/analyzer/sm-taint.cc @@ -830,13 +830,11 @@ taint_state_machine::on_condition (sm_context *sm_ctxt, const gimple *stmt, const svalue *lhs, enum tree_code op, - const svalue *rhs ATTRIBUTE_UNUSED) const + const svalue *rhs) const { if (stmt == NULL) return; - // TODO: this doesn't use the RHS; should we make it symmetric? - // TODO switch (op) { @@ -845,10 +843,17 @@ taint_state_machine::on_condition (sm_context *sm_ctxt, case GE_EXPR: case GT_EXPR: { + /* (LHS >= RHS) or (LHS > RHS) + LHS gains a lower bound + RHS gains an upper bound. */ sm_ctxt->on_transition (node, stmt, lhs, m_tainted, m_has_lb); sm_ctxt->on_transition (node, stmt, lhs, m_has_ub, m_stop); + sm_ctxt->on_transition (node, stmt, rhs, m_tainted, + m_has_ub); + sm_ctxt->on_transition (node, stmt, rhs, m_has_lb, + m_stop); } break; case LE_EXPR: @@ -896,10 +901,17 @@ taint_state_machine::on_condition (sm_context *sm_ctxt, } } + /* (LHS <= RHS) or (LHS < RHS) + LHS gains an upper bound + RHS gains a lower bound. */ sm_ctxt->on_transition (node, stmt, lhs, m_tainted, m_has_ub); sm_ctxt->on_transition (node, stmt, lhs, m_has_lb, m_stop); + sm_ctxt->on_transition (node, stmt, rhs, m_tainted, + m_has_lb); + sm_ctxt->on_transition (node, stmt, rhs, m_has_ub, + m_stop); } break; default: diff --git a/gcc/testsuite/gcc.dg/analyzer/torture/taint-read-index-3.c b/gcc/testsuite/gcc.dg/analyzer/torture/taint-read-index-3.c new file mode 100644 index 00000000000..8eb6061a08b --- /dev/null +++ b/gcc/testsuite/gcc.dg/analyzer/torture/taint-read-index-3.c @@ -0,0 +1,52 @@ +// TODO: remove need for the taint option: +/* { dg-additional-options "-fanalyzer-checker=taint" } */ +/* { dg-skip-if "" { *-*-* } { "-fno-fat-lto-objects" } { "" } } */ + +struct raw_ep { + /* ...snip... */ + int state; + /* ...snip... */ +}; + +struct raw_dev { + /* ...snip... */ + struct raw_ep eps[30]; + int eps_num; + /* ...snip... */ +}; + +int __attribute__((tainted_args)) +simplified_raw_ioctl_ep_disable(struct raw_dev *dev, unsigned long value) +{ + int ret = 0, i = value; + + if (i < 0 || i >= dev->eps_num) { + ret = -16; + goto out_unlock; + } + if (dev->eps[i].state == 0) { /* { dg-bogus "attacker-controlled" } */ + ret = -22; + goto out_unlock; + } + +out_unlock: + return ret; +} + +int __attribute__((tainted_args)) +test_2(struct raw_dev *dev, int i) +{ + int ret = 0; + + if (i < 0 || i >= dev->eps_num) { + ret = -16; + goto out_unlock; + } + if (dev->eps[i].state == 0) { /* { dg-bogus "attacker-controlled" } */ + ret = -22; + goto out_unlock; + } + +out_unlock: + return ret; +}
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