Messages in this thread Patch in this message |  | | From | Wen Yang <> | Subject | [PATCH v2] coccinelle: semantic patch to check for inappropriate do_div() calls | Date | Wed, 8 Jan 2020 01:02:40 +0800 |
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do_div() does a 64-by-32 division. When the divisor is unsigned long, u64, or s64, do_div() truncates it to 32 bits, this means it can test non-zero and be truncated to zero for division. This semantic patch is inspired by Mateusz Guzik's patch: commit b0ab99e7736a ("sched: Fix possible divide by zero in avg_atom() calculation")
Signed-off-by: Wen Yang <wenyang@linux.alibaba.com> Cc: Julia Lawall <julia.lawall@inria.fr> Cc: Gilles Muller <Gilles.Muller@lip6.fr> Cc: Nicolas Palix <nicolas.palix@imag.fr> Cc: Michal Marek <michal.lkml@markovi.net> Cc: Matthias Maennich <maennich@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: cocci@systeme.lip6.fr Cc: linux-kernel@vger.kernel.org --- v2: - add a special case for constants and checking whether the value is obviously safe and no warning is needed. - fix 'WARNING:' twice in each case. - extend the warning to say "consider using div64_xxx instead".
scripts/coccinelle/misc/do_div.cocci | 169 +++++++++++++++++++++++++++ 1 file changed, 169 insertions(+) create mode 100644 scripts/coccinelle/misc/do_div.cocci
diff --git a/scripts/coccinelle/misc/do_div.cocci b/scripts/coccinelle/misc/do_div.cocci new file mode 100644 index 000000000000..0fd904b9157f --- /dev/null +++ b/scripts/coccinelle/misc/do_div.cocci @@ -0,0 +1,169 @@ +// SPDX-License-Identifier: GPL-2.0-only +/// do_div() does a 64-by-32 division. +/// When the divisor is long, unsigned long, u64, or s64, +/// do_div() truncates it to 32 bits, this means it can test +/// non-zero and be truncated to 0 for division on 64bit platforms. +/// +//# This makes an effort to find those inappropriate do_div() calls. +// +// Confidence: Moderate +// Copyright: (C) 2020 Wen Yang, Alibaba. +// Comments: +// Options: --no-includes --include-headers + +virtual context +virtual org +virtual report + +@initialize:python@ +@@ + +def get_digit_type_and_value(str): + is_digit = False + value = 0 + + try: + if (str.isdigit()): + is_digit = True + value = int(str, 0) + elif (str.upper().endswith('ULL')): + is_digit = True + value = int(str[:-3], 0) + elif (str.upper().endswith('LL')): + is_digit = True + value = int(str[:-2], 0) + elif (str.upper().endswith('UL')): + is_digit = True + value = int(str[:-2], 0) + elif (str.upper().endswith('L')): + is_digit = True + value = int(str[:-1], 0) + elif (str.upper().endswith('U')): + is_digit = True + value = int(str[:-1], 0) + except Exception as e: + print('Error:',e) + is_digit = False + value = 0 + finally: + return is_digit, value + +def construct_warnings(str, suggested_fun): + msg="WARNING: do_div() does a 64-by-32 division, please consider using %s instead." + is_digit, value = get_digit_type_and_value(str) + if (is_digit): + if (value >= 0x100000000): + return msg %(suggested_fun) + else: + return None + else: + return msg % suggested_fun + +@depends on context@ +expression f; +long l; +unsigned long ul; +u64 ul64; +s64 sl64; + +@@ +( +* do_div(f, l); +| +* do_div(f, ul); +| +* do_div(f, ul64); +| +* do_div(f, sl64); +) + +@r depends on (org || report)@ +expression f; +long l; +unsigned long ul; +position p; +u64 ul64; +s64 sl64; +@@ +( +do_div@p(f, l); +| +do_div@p(f, ul); +| +do_div@p(f, ul64); +| +do_div@p(f, sl64); +) + +@script:python depends on org@ +p << r.p; +ul << r.ul; +@@ + +warnings = construct_warnings(ul, "div64_ul") +if warnings != None: + coccilib.org.print_todo(p[0], warnings) + +@script:python depends on org@ +p << r.p; +l << r.l; +@@ + +warnings = construct_warnings(l, "div64_long") +if warnings != None: + coccilib.org.print_todo(p[0], warnings) + +@script:python depends on org@ +p << r.p; +ul64 << r.ul64; +@@ + +warnings = construct_warnings(ul64, "div64_u64") +if warnings != None: + coccilib.org.print_todo(p[0], warnings) + +@script:python depends on org@ +p << r.p; +sl64 << r.sl64; +@@ + +warnings = construct_warnings(sl64, "div64_s64") +if warnings != None: + coccilib.org.print_todo(p[0], warnings) + + +@script:python depends on report@ +p << r.p; +ul << r.ul; +@@ + +warnings = construct_warnings(ul, "div64_ul") +if warnings != None: + coccilib.report.print_report(p[0], warnings) + +@script:python depends on report@ +p << r.p; +l << r.l; +@@ + +warnings = construct_warnings(l, "div64_long") +if warnings != None: + coccilib.report.print_report(p[0], warnings) + +@script:python depends on report@ +p << r.p; +sl64 << r.sl64; +@@ + +warnings = construct_warnings(sl64, "div64_s64") +if warnings != None: + coccilib.report.print_report(p[0], warnings) + +@script:python depends on report@ +p << r.p; +ul64 << r.ul64; +@@ + +warnings = construct_warnings(ul64, "div64_u64") +if warnings != None: + coccilib.report.print_report(p[0], warnings) -- 2.23.0
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