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busybox: patch CVE-2026-38754
Pick patch which fixes this CVE as discussed in [1]. [1] https://lists.busybox.net/pipermail/busybox/2026-July/092392.html (From OE-Core rev: 8cabc0b083bb9e152803ef9e92ff5ae11459f00f) Signed-off-by: Peter Marko <peter.marko@siemens.com> Signed-off-by: Fabien Thomas <fabien.thomas@smile.fr> Signed-off-by: Paul Barker <paul@pbarker.dev>
This commit is contained in:
Peter Marko
155
meta/recipes-core/busybox/busybox/CVE-2026-38754.patch
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155
meta/recipes-core/busybox/busybox/CVE-2026-38754.patch
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From a448b6d5b21e5b21249391389b6f0551d9bea136 Mon Sep 17 00:00:00 2001
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From: Sanghyun Park <sanghyun.park.cnu@gmail.com>
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Date: Thu, 18 Jun 2026 17:04:20 +0900
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Subject: [PATCH] ash: fix out-of-bounds read in ifsbreakup()
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ifsfree() does not only release allocated ifsregion nodes; it also clears
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the global IFS region state used by ifsbreakup(). If argstr() raises an
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error while expanding an argument, ash longjmps out of expandarg() before
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that cleanup runs, leaving stale IFS split offsets behind.
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A later expansion can reuse the stack for a shorter string. ifsbreakup()
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then sees the stale IFS state, trusts the old offsets, and can walk past
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the current stack block before dereferencing p.
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Follow dash's root-cause fix: when an expansion-related handler catches
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EXERROR and continues, restore the handler and call ifsfree(). Apply
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the cleanup to redirectsafe(), expandstr(), and evaltree().
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Upstream commit:
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Date: Mon Dec 5 23:02:01 2022 +0800
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expand: Add ifsfree to expand to fix a logic error that causes a buffer over-read
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On Mon, Jun 20, 2022 at 02:27:10PM -0400, Alex Gorinson wrote:
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> Due to a logic error in the ifsbreakup function in expand.c if a
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> heredoc and normal command is run one after the other by means of a
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> semi-colon, when the second command drops into ifsbreakup the command
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> will be evaluated with the ifslastp/ifsfirst struct that was set when
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> the here doc was evaluated. This results in a buffer over-read that
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> can leak the program's heap, stack, and arena addresses which can be
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> used to beat ASLR.
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>
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> Steps to Reproduce:
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> First bug:
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> cmd args: ~/exampleDir/example> dash
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> $ M='AAAAAAAAAAAAAAAAA' <note: 17 A's>
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> $ q00(){
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> $ <<000;echo
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> $ ${D?$M$M$M$M$M$M} <note: 6 $M's>
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> $ 000
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> $ }
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> $ q00 <note: After the q00 is typed in, the leak
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> should be echo'd out; this works with ash, busybox ash, and dash and
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> with all option args.>
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>
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> Patch:
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> Adding the following to expand.c will fix both bugs in one go.
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> (Thank you to Harald van Dijk and Michael Greenberg for doing the
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> heavy lifting for this patch!)
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> ==========================
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> --- a/src/expand.c
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> +++ b/src/expand.c
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> @@ -859,6 +859,7 @@
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> if (discard)
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> return -1;
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>
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> +ifsfree();
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> sh_error("Bad substitution");
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> }
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>
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> @@ -1739,6 +1740,7 @@
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> } else
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> msg = umsg;
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> }
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> +ifsfree();
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> sh_error("%.*s: %s%s", end - var - 1, var, msg, tail);
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> }
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> ==========================
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Thanks for the report!
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I think it's better to add the ifsfree() call to the exception
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handling path as other sh_error calls may trigger this too.
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function old new delta
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restore_handler_expandarg - 33 +33
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evaltree 725 711 -14
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static.redirectsafe 141 124 -17
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expandstr 262 242 -20
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------------------------------------------------------------------------------
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(add/remove: 1/0 grow/shrink: 0/3 up/down: 36/-45) Total: -18 bytes
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Signed-off-by: Sanghyun Park <sanghyun.park.cnu@gmail.com>
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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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CVE: CVE-2026-38754
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Upstream-Status: Backport [https://github.com/vda-linux/busybox_mirror/commit/a448b6d5b21e5b21249391389b6f0551d9bea136]
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Signed-off-by: Peter Marko <peter.marko@siemens.com>
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---
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shell/ash.c | 24 +++++++++++++++---------
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1 file changed, 15 insertions(+), 9 deletions(-)
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diff --git a/shell/ash.c b/shell/ash.c
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index fb887f31b..b8ff67b16 100644
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--- a/shell/ash.c
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+++ b/shell/ash.c
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@@ -5480,6 +5480,7 @@ stoppedjobs(void)
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*/
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/* openhere needs this forward reference */
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static void expandhere(union node *arg);
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+static void ifsfree(void);
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static int
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openhere(union node *redir)
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{
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@@ -5909,6 +5910,17 @@ redirect(union node *redir, int flags)
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// preverrout_fd = copied_fd2;
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}
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+static void
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+restore_handler_expandarg(struct jmploc *savehandler, int err)
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+{
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+ exception_handler = savehandler;
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+ if (err) {
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+ if (exception_type != EXERROR)
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+ longjmp(exception_handler->loc, 1);
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+ ifsfree();
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+ }
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+}
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+
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static int
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redirectsafe(union node *redir, int flags)
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{
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@@ -5924,9 +5936,7 @@ redirectsafe(union node *redir, int flags)
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exception_handler = &jmploc;
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redirect(redir, flags);
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}
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- exception_handler = savehandler;
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- if (err && exception_type != EXERROR)
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- longjmp(exception_handler->loc, 1);
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+ restore_handler_expandarg(savehandler, err);
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RESTORE_INT(saveint);
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return err;
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}
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@@ -9435,9 +9445,7 @@ evaltree(union node *n, int flags)
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trap_depth--;
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in_trap_ERR = 0;
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- exception_handler = savehandler;
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- if (err && exception_type != EXERROR)
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- longjmp(exception_handler->loc, 1);
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+ restore_handler_expandarg(savehandler, err);
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exitstatus = savestatus;
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}
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@@ -13444,9 +13452,7 @@ expandstr(const char *ps, int syntax_type)
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result = stackblock();
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out:
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- exception_handler = savehandler;
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- if (err && exception_type != EXERROR)
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- longjmp(exception_handler->loc, 1);
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+ restore_handler_expandarg(savehandler, err);
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doprompt = saveprompt;
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/* Try: PS1='`xxx(`' */
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@@ -66,6 +66,7 @@ SRC_URI = "https://busybox.net/downloads/busybox-${PV}.tar.bz2;name=tarball \
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file://CVE-2026-26157-CVE-2026-26158-02.patch \
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file://CVE-2026-29004-01.patch \
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file://CVE-2026-29004-02.patch \
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file://CVE-2026-38754.patch \
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"
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SRC_URI:append:libc-musl = " file://musl.cfg "
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# TODO http://lists.busybox.net/pipermail/busybox/2023-January/090078.html
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