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From: "clopez at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug analyzer/108719] New: RFE: allow specifying argument indexes
 for __attribute__((tainted_args))
Date: Wed, 08 Feb 2023 15:25:43 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: analyzer
X-Bugzilla-Version: 13.0
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: clopez at suse dot de
X-Bugzilla-Status: UNCONFIRMED
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X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: dmalcolm at gcc dot gnu.org
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108719

            Bug ID: 108719
           Summary: RFE: allow specifying argument indexes for
                    __attribute__((tainted_args))
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: analyzer
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: clopez at suse dot de
  Target Milestone: ---

Consider allowing developers to specify which function arguments are tainte=
d,
very much like the nonnull attribute, e.g.:

    __attribute__((tainted_args (2, 3)))

When no indexes are specified, all arguments should be considered tainted -
this is the behavior currently implemented.

Specifically, there is a common pattern for callbacks where the first argum=
ent
corresponds to untainted data (often either a structure provided by caller =
of
the callback or some opaque pointer requested by the callee). A prime examp=
le
of this are Linux device drivers, where the first parameter is a
kernel-provided structure:

    struct file_operations {
        ...
        ssize_t (*read) (struct file *, char *, size_t, loff_t *);
        ssize_t (*write) (struct file *, const char *, size_t, loff_t *);
        ...
    }

Another example would be qemu MMIO callbacks:

    struct MemoryRegionOps {
        uint64_t (*read)(void *opaque, hwaddr addr, unsigned size);
        void (*write)(void *opaque, hwaddr addr, uint64_t data, unsigned si=
ze);
        ...
    }=