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* [Bug analyzer/106373] New: False positives from -Wanalyzer-tainted-array-index with casts
@ 2022-07-20 18:09 dmalcolm at gcc dot gnu.org
2022-07-20 19:06 ` [Bug analyzer/106373] False positives from -Wanalyzer-tainted-array-index on comparison with non-const dmalcolm at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: dmalcolm at gcc dot gnu.org @ 2022-07-20 18:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106373
Bug ID: 106373
Summary: False positives from -Wanalyzer-tainted-array-index
with casts
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: analyzer
Assignee: dmalcolm at gcc dot gnu.org
Reporter: dmalcolm at gcc dot gnu.org
Blocks: 106358
Target Milestone: ---
See: https://godbolt.org/z/P5nGMohxd
Am seeing false positive with -O1 -fanalyzer -fanalyzer-checker=taint on this
code:
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) {
ret = -22;
goto out_unlock;
}
out_unlock:
return ret;
}
../../src/raw_gadget.c: In function ‘simplified_raw_ioctl_ep_disable’:
../../src/raw_gadget.c:23:18: warning: use of attacker-controlled value ‘value’
in array lookup without upper-bounds checking [CWE-129]
[-Wanalyzer-tainted-array-index]
23 | if (dev->eps[i].state == 0) {
| ~~~~~~~~~~~^~~~~~
‘simplified_raw_ioctl_ep_disable’: event 1
|
| 15 | simplified_raw_ioctl_ep_disable(struct raw_dev *dev, unsigned long
value)
| | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| | |
| | (1) function ‘simplified_raw_ioctl_ep_disable’ marked with
‘__attribute__((tainted_args))’
|
+--> ‘simplified_raw_ioctl_ep_disable’: events 2-5
|
| 15 | simplified_raw_ioctl_ep_disable(struct raw_dev *dev,
unsigned long value)
| | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| | |
| | (2) entry to ‘simplified_raw_ioctl_ep_disable’
|......
| 19 | if (i < 0 || i >= dev->eps_num) {
| | ~
| | |
| | (3) following ‘false’ branch...
|......
| 23 | if (dev->eps[i].state == 0) {
| | ~~~~~~~~~~~~~~~~~
| | |
| | (4) ...to here
| | (5) use of attacker-controlled value
‘value’ in array lookup without upper-bounds checking
|
Seems to need at least -O1.
Reduced from false positives seen in various ioctl handlers in Linux kernel in
drivers/usb/gadget/legacy/raw_gadget.c (with "allyesconfig").
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106358
[Bug 106358] [meta-bug] tracker bug for building the Linux kernel with
-fanalyzer
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug analyzer/106373] False positives from -Wanalyzer-tainted-array-index on comparison with non-const
2022-07-20 18:09 [Bug analyzer/106373] New: False positives from -Wanalyzer-tainted-array-index with casts dmalcolm at gcc dot gnu.org
@ 2022-07-20 19:06 ` dmalcolm at gcc dot gnu.org
2022-07-20 21:28 ` cvs-commit at gcc dot gnu.org
2022-07-20 21:32 ` dmalcolm at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: dmalcolm at gcc dot gnu.org @ 2022-07-20 19:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106373
David Malcolm <dmalcolm at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Last reconfirmed| |2022-07-20
Status|UNCONFIRMED |ASSIGNED
Summary|False positives from |False positives from
|-Wanalyzer-tainted-array-in |-Wanalyzer-tainted-array-in
|dex with casts |dex on comparison with
| |non-const
--- Comment #1 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
The issue isn't the casts; it's the comparison against non-const, which looks
like:
_1 = dev_6(D)->eps_num;
if (_1 <= i_4(D))
at the gimple level, and where i_4(D) is on the RHS, and sm-taint.cc is only
looking at comparisons of the LHS.
I'm testing a fix.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug analyzer/106373] False positives from -Wanalyzer-tainted-array-index on comparison with non-const
2022-07-20 18:09 [Bug analyzer/106373] New: False positives from -Wanalyzer-tainted-array-index with casts dmalcolm at gcc dot gnu.org
2022-07-20 19:06 ` [Bug analyzer/106373] False positives from -Wanalyzer-tainted-array-index on comparison with non-const dmalcolm at gcc dot gnu.org
@ 2022-07-20 21:28 ` cvs-commit at gcc dot gnu.org
2022-07-20 21:32 ` dmalcolm at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-07-20 21:28 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106373
--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>:
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>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug analyzer/106373] False positives from -Wanalyzer-tainted-array-index on comparison with non-const
2022-07-20 18:09 [Bug analyzer/106373] New: False positives from -Wanalyzer-tainted-array-index with casts dmalcolm at gcc dot gnu.org
2022-07-20 19:06 ` [Bug analyzer/106373] False positives from -Wanalyzer-tainted-array-index on comparison with non-const dmalcolm at gcc dot gnu.org
2022-07-20 21:28 ` cvs-commit at gcc dot gnu.org
@ 2022-07-20 21:32 ` dmalcolm at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: dmalcolm at gcc dot gnu.org @ 2022-07-20 21:32 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106373
David Malcolm <dmalcolm at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #3 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Should be fixed on trunk by the above patch.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-07-20 18:09 [Bug analyzer/106373] New: False positives from -Wanalyzer-tainted-array-index with casts dmalcolm at gcc dot gnu.org
2022-07-20 19:06 ` [Bug analyzer/106373] False positives from -Wanalyzer-tainted-array-index on comparison with non-const dmalcolm at gcc dot gnu.org
2022-07-20 21:28 ` cvs-commit at gcc dot gnu.org
2022-07-20 21:32 ` dmalcolm at gcc dot gnu.org
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