* [PATCH] Undefined behavior reported in copy_bitwise @ 2020-04-09 23:50 krokus 2020-04-10 14:59 ` Simon Marchi 0 siblings, 1 reply; 5+ messages in thread From: krokus @ 2020-04-09 23:50 UTC (permalink / raw) To: gdb-patches gdb version 9.1, built with clang 8.0.0 on Ubuntu 18.04 (x86_64); --enable-ubsan (for clang's undefined behavior sanitizer) Executing command; `maint selftest copy_bitwise` bombs in runtime error: ../../gdb/utils.c:3432:28: runtime error: left shift of negative value -1 Closer look reveals the offending shift: `(~0 << nbits)`, apparently 0 is treated as signed int, resulting in negative complement. Explicitly stating it unsigned 0U fixes it and the `copy_bitwise` test passes ok. patch -p1: ```````` --- gdb/utils.c 2020-04-09 18:41:03.339065535 -0500 +++ gdb/utils.c 2020-04-09 18:41:24.427064851 -0500 @@ -3429,7 +3429,7 @@ buf |= *source << avail; buf &= (1 << nbits) - 1; - *dest = (*dest & (~0 << nbits)) | buf; + *dest = (*dest & (~0U << nbits)) | buf; } } ```````` ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] Undefined behavior reported in copy_bitwise 2020-04-09 23:50 [PATCH] Undefined behavior reported in copy_bitwise krokus @ 2020-04-10 14:59 ` Simon Marchi 2020-04-10 20:56 ` krokus 0 siblings, 1 reply; 5+ messages in thread From: Simon Marchi @ 2020-04-10 14:59 UTC (permalink / raw) To: krokus, gdb-patches On 2020-04-09 7:50 p.m., krokus via Gdb-patches wrote: > gdb version 9.1, built with clang 8.0.0 on Ubuntu 18.04 (x86_64); > --enable-ubsan (for clang's undefined behavior sanitizer) > > Executing command; `maint selftest copy_bitwise` bombs in runtime error: > ../../gdb/utils.c:3432:28: runtime error: left shift of negative value -1 > > Closer look reveals the offending shift: `(~0 << nbits)`, apparently 0 > is treated as signed int, resulting in negative complement. Explicitly > stating it unsigned 0U fixes it and the `copy_bitwise` test passes > ok. > > patch -p1: > ```````` > --- gdb/utils.c 2020-04-09 18:41:03.339065535 -0500 > +++ gdb/utils.c 2020-04-09 18:41:24.427064851 -0500 > @@ -3429,7 +3429,7 @@ > buf |= *source << avail; > > buf &= (1 << nbits) - 1; > - *dest = (*dest & (~0 << nbits)) | buf; > + *dest = (*dest & (~0U << nbits)) | buf; > } > } > ```````` > Thanks. I'll try to reproduce it, but at first sight it seems fine. Could you please provide a ChangeLog entry for this, with the name and email address you'd like to have in there? See the gdb/ChangeLog file for examples. Simon ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] Undefined behavior reported in copy_bitwise 2020-04-10 14:59 ` Simon Marchi @ 2020-04-10 20:56 ` krokus 2020-04-10 21:24 ` Simon Marchi 0 siblings, 1 reply; 5+ messages in thread From: krokus @ 2020-04-10 20:56 UTC (permalink / raw) To: gdb-patches Simon, > Could you please provide a ChangeLog entry for this, with the name and > email address you'd like to have in there? Will do. Do I need to update the ChangeLog myself or you could do this with my entry? I'm not set up for repo commit access. ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] Undefined behavior reported in copy_bitwise 2020-04-10 20:56 ` krokus @ 2020-04-10 21:24 ` Simon Marchi 2020-04-11 1:08 ` Simon Marchi 0 siblings, 1 reply; 5+ messages in thread From: Simon Marchi @ 2020-04-10 21:24 UTC (permalink / raw) To: krokus, gdb-patches On 2020-04-10 4:56 p.m., krokus via Gdb-patches wrote: > Simon, > >> Could you please provide a ChangeLog entry for this, with the name and >> email address you'd like to have in there? > > Will do. > Do I need to update the ChangeLog myself or you could do this with my entry? > I'm not set up for repo commit access. > Just provide it here in the email body, I'll take care of formatting and pushing the patch. Thanks, Simon ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] Undefined behavior reported in copy_bitwise 2020-04-10 21:24 ` Simon Marchi @ 2020-04-11 1:08 ` Simon Marchi 0 siblings, 0 replies; 5+ messages in thread From: Simon Marchi @ 2020-04-11 1:08 UTC (permalink / raw) To: krokus, gdb-patches On 2020-04-10 5:24 p.m., Simon Marchi wrote: > On 2020-04-10 4:56 p.m., krokus via Gdb-patches wrote: >> Simon, >> >>> Could you please provide a ChangeLog entry for this, with the name and >>> email address you'd like to have in there? >> >> Will do. >> Do I need to update the ChangeLog myself or you could do this with my entry? >> I'm not set up for repo commit access. >> > > Just provide it here in the email body, I'll take care of formatting and pushing > the patch. Thanks, I've pushed the patch as below. I've modified the ChangeLog entry a bit to more clearly state what changed in the affected function, but that's it. From cf83625da29d1239e97f1eb4d145f347cb741889 Mon Sep 17 00:00:00 2001 From: Artur Shepilko <nomadbyte@gmail.com> Date: Fri, 10 Apr 2020 10:56:43 -0400 Subject: [PATCH] gdb: fix undefined behavior reported in copy_bitwise gdb version 9.1, built with clang 8.0.0 on Ubuntu 18.04 (x86_64); --enable-ubsan (for clang's undefined behavior sanitizer) Executing command; `maint selftest copy_bitwise` bombs in runtime error: ../../gdb/utils.c:3432:28: runtime error: left shift of negative value -1 Closer look reveals the offending shift: `(~0 << nbits)`, apparently 0 is treated as signed int, resulting in negative complement. Explicitly stating it unsigned 0U fixes it and the `copy_bitwise` test passes ok. --- gdb/ChangeLog | 5 +++++ gdb/utils.c | 2 +- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 661a41467bbe..81102ee569bc 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2020-04-10 Artur Shepilko <nomadbyte@gmail.com> + + * utils.c (copy_bitwise): Use unsigned 0 constant as operand of + bit shift. + 2020-04-10 Tom Tromey <tromey@adacore.com> * symfile.c (symbol_file_add_separate): Preserve OBJF_MAINLINE. diff --git a/gdb/utils.c b/gdb/utils.c index bda6bbf5b0e7..f5b20331b1e2 100644 --- a/gdb/utils.c +++ b/gdb/utils.c @@ -3433,7 +3433,7 @@ copy_bitwise (gdb_byte *dest, ULONGEST dest_offset, buf |= *source << avail; buf &= (1 << nbits) - 1; - *dest = (*dest & (~0 << nbits)) | buf; + *dest = (*dest & (~0U << nbits)) | buf; } } -- 2.26.0 ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2020-04-11 1:08 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-04-09 23:50 [PATCH] Undefined behavior reported in copy_bitwise krokus 2020-04-10 14:59 ` Simon Marchi 2020-04-10 20:56 ` krokus 2020-04-10 21:24 ` Simon Marchi 2020-04-11 1:08 ` Simon Marchi
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).