diff options
| author | Jilles Tjoelker <jilles@FreeBSD.org> | 2025-11-15 16:43:03 +0000 |
|---|---|---|
| committer | Jilles Tjoelker <jilles@FreeBSD.org> | 2025-11-17 18:32:38 +0000 |
| commit | 75a6c38e4d5c651b7398bf2bea5baa41a0939e92 (patch) | |
| tree | b05ad4358167b4bb653631f52292217241e5deef | |
| parent | 33383fbf606be619af0e107106f4f6028c9eab0d (diff) | |
sh: Fix a double free in a rare scenario with pipes
The command
sh -c 'sleep 3 | sleep 2 & sleep 3 & kill %1; wait %1'
crashes (with appropriate sanitization such as putting
MALLOC_CONF=abort:true,junk:true in the environment or compiling with
-fsanitize=address).
What happens here is that waitcmdloop() calls dowait() with a NULL job
pointer, instructing dowait() to freejob() if it's a non-interactive
shell and $! was not and cannot be referenced for it. However,
waitcmdloop() then uses fields possibly freed by freejob() and calls
freejob() again.
This only occurs if the job being waited for is identified via % syntax
($! has never been referenced for it), it is a pipeline with two or more
elements and another background job has been started before the wait
command. That seems special enough for a bug to remain. Test scripts
written by Jilles would almost always use $! and not % syntax.
We can instead make waitcmdloop() pass its job pointer to dowait(),
fixing up things for that (waitcmdloop() will have to call deljob() if
it does not call freejob()).
The crash from
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=290330#c2 appears to
be the same bug.
PR: 290330
Reported by: bdrewery
Reviewed by: bdrewery
Differential Revision: https://reviews.freebsd.org/D53773
| -rw-r--r-- | bin/sh/jobs.c | 3 | ||||
| -rw-r--r-- | bin/sh/tests/builtins/Makefile | 1 | ||||
| -rw-r--r-- | bin/sh/tests/builtins/wait11.0 | 6 |
3 files changed, 9 insertions, 1 deletions
diff --git a/bin/sh/jobs.c b/bin/sh/jobs.c index 1328ae50edef..0aaff5e1e140 100644 --- a/bin/sh/jobs.c +++ b/bin/sh/jobs.c @@ -573,6 +573,7 @@ waitcmdloop(struct job *job) freejob(job); else { job->remembered = 0; + deljob(job); if (job == bgjob) bgjob = NULL; } @@ -599,7 +600,7 @@ waitcmdloop(struct job *job) break; } } - } while (dowait(DOWAIT_BLOCK | DOWAIT_SIG, (struct job *)NULL) != -1); + } while (dowait(DOWAIT_BLOCK | DOWAIT_SIG, job) != -1); sig = pendingsig_waitcmd; pendingsig_waitcmd = 0; diff --git a/bin/sh/tests/builtins/Makefile b/bin/sh/tests/builtins/Makefile index 7fdecb23c817..407d2aeaa061 100644 --- a/bin/sh/tests/builtins/Makefile +++ b/bin/sh/tests/builtins/Makefile @@ -188,5 +188,6 @@ ${PACKAGE}FILES+= wait7.0 ${PACKAGE}FILES+= wait8.0 ${PACKAGE}FILES+= wait9.127 ${PACKAGE}FILES+= wait10.0 +${PACKAGE}FILES+= wait11.0 .include <bsd.test.mk> diff --git a/bin/sh/tests/builtins/wait11.0 b/bin/sh/tests/builtins/wait11.0 new file mode 100644 index 000000000000..d5fab26fb677 --- /dev/null +++ b/bin/sh/tests/builtins/wait11.0 @@ -0,0 +1,6 @@ +sleep 3 | sleep 2 & +sleep 3 & +kill %1 +wait %1 +r=$? +[ "$r" -gt 128 ] && [ "$(kill -l "$r")" = TERM ] |