Date: Fri, 8 Jan 2021 22:37:45 GMT From: Bryan Drewery <bdrewery@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: f222a6b88614 - main - dtrace: Fix /"string" == NULL/ comparisons using an uninitialized value. Message-ID: <202101082237.108MbjU1068611@gitrepo.freebsd.org>
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The branch main has been updated by bdrewery: URL: https://cgit.FreeBSD.org/src/commit/?id=f222a6b88614db13ae83c8110281e690d1381a4c commit f222a6b88614db13ae83c8110281e690d1381a4c Author: Bryan Drewery <bdrewery@FreeBSD.org> AuthorDate: 2020-12-18 17:58:03 +0000 Commit: Bryan Drewery <bdrewery@FreeBSD.org> CommitDate: 2021-01-08 22:37:17 +0000 dtrace: Fix /"string" == NULL/ comparisons using an uninitialized value. A test of this is funcs/tst.strtok.d which has this filter: BEGIN /(this->field = strtok(this->str, ",")) == NULL/ { exit(1); } The test will randomly fail with exit status of 1 indicating that this->field was NULL even though printing it out shows it is not. This is compiled to the DTrace instruction set: // Pushed arguments not shown here // call strtok() and set result into %r1 07: 2f001f01 call DIF_SUBR(31), %r1 ! strtok // set thread local scalar this->field from %r1 08: 39050101 stls %r1, DT_VAR(1281) ! DT_VAR(1281) = "field" // Prepare for the == comparison // Set right side of %r2 to NULL 09: 25000102 setx DT_INTEGER[1], %r2 ! 0x0 // string compare %r1 (strtok result) to %r2 10: 27010200 scmp %r1, %r2 In this case only %r1 is loaded with a string limit set to lim1. %r2 being NULL does not get loaded and does not set lim2. Then we call dtrace_strncmp() with MIN(lim1, lim2) resulting in passing 0 and comparing neither side. dtrace_strncmp() handles this case fine and it already has been while being lucky with what lim2 was [un]initialized as. Reviewed by: markj, Don Morris <dgmorris AT earthlink.net> Sponsored by: Dell EMC Differential Revision: https://reviews.freebsd.org/D27671 --- sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c | 8 ++++++++ sys/modules/dtrace/dtrace/Makefile | 1 - 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c b/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c index 3d68a68ba819..b212185a4578 100644 --- a/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c +++ b/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c @@ -6374,6 +6374,14 @@ dtrace_dif_emulate(dtrace_difo_t *difo, dtrace_mstate_t *mstate, uintptr_t s2 = regs[r2]; size_t lim1, lim2; + /* + * If one of the strings is NULL then the limit becomes + * 0 which compares 0 characters in dtrace_strncmp() + * resulting in a false positive. dtrace_strncmp() + * treats a NULL as an empty 1-char string. + */ + lim1 = lim2 = 1; + if (s1 != 0 && !dtrace_strcanload(s1, sz, &lim1, mstate, vstate)) break; diff --git a/sys/modules/dtrace/dtrace/Makefile b/sys/modules/dtrace/dtrace/Makefile index 80278fc83a32..55f9f4f66f36 100644 --- a/sys/modules/dtrace/dtrace/Makefile +++ b/sys/modules/dtrace/dtrace/Makefile @@ -61,6 +61,5 @@ CFLAGS+= -include ${SYSDIR}/cddl/compat/opensolaris/sys/debug_compat.h CFLAGS.dtrace_asm.S+= -D_SYS_ERRNO_H_ -D_SYS_PARAM_H_ -DLOCORE CWARNFLAGS+= ${OPENZFS_CWARNFLAGS} CWARNFLAGS+= -Wno-parentheses -CWARNFLAGS+= -Wno-uninitialized CWARNFLAGS+= -Wno-cast-qual CWARNFLAGS+= -Wno-unused
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