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| author | Sören Tempel | 2022-02-28 08:36:50 +0100 |
|---|---|---|
| committer | Denys Vlasenko | 2022-03-01 08:47:43 +0100 |
| commit | fa52ac9781f479de8ab4d8526276244c0a0471f4 (patch) | |
| tree | a1cf6cad888fa4e22dd160b334e53854562cba47 | |
| parent | 1891fdda59092a215d3a407d9108bbbe6ab8df7a (diff) | |
| download | busybox-fa52ac9781f479de8ab4d8526276244c0a0471f4.zip busybox-fa52ac9781f479de8ab4d8526276244c0a0471f4.tar.gz | |
ash: don't read past end of var in subvareval for bash substitutions
Without this patch, BusyBox handles bash pattern substitutions without
a terminating '/' character incorrectly.
Consider the following shell script:
_bootstrapver=5.0.211-r0
_referencesdir="/usr/${_bootstrapver/-*}/Sources"
echo $_referencesdir
This should output `/usr/5.0.211/Sources`. However, without this patch
it instead outputs `/usr/5.0.211Sources`. This is due to the fact that
BusyBox expects the bash pattern substitutions to always be terminated
with a '/' (at least in this part of subvareval) and thus reads passed
the substitution itself and consumes the '/' character which is part of
the literal string. If there is no '/' after the substitution then
BusyBox might perform an out-of-bounds read under certain circumstances.
When replacing the bash pattern substitution with `${_bootstrapver/-*/}`,
or with this patch applied, ash outputs the correct value.
Signed-off-by: Sören Tempel <soeren@soeren-tempel.net>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
5 files changed, 10 insertions, 0 deletions
diff --git a/shell/ash.c b/shell/ash.c index adb0f22..54335c5 100644 --- a/shell/ash.c +++ b/shell/ash.c @@ -7081,6 +7081,10 @@ subevalvar(char *start, char *str, int strloc, *repl = '\0'; break; } + if ((unsigned char)*repl == CTLENDVAR) { /* ${v/pattern} (no trailing /, no repl) */ + repl = NULL; + break; + } /* Handle escaped slashes, e.g. "${v/\//_}" (they are CTLESC'ed by this point) */ if ((unsigned char)*repl == CTLESC && repl[1]) repl++; diff --git a/shell/ash_test/ash-vars/var_bash_repl_unterminated.right b/shell/ash_test/ash-vars/var_bash_repl_unterminated.right new file mode 100644 index 0000000..5bff3a6 --- /dev/null +++ b/shell/ash_test/ash-vars/var_bash_repl_unterminated.right @@ -0,0 +1 @@ +b/d diff --git a/shell/ash_test/ash-vars/var_bash_repl_unterminated.tests b/shell/ash_test/ash-vars/var_bash_repl_unterminated.tests new file mode 100755 index 0000000..c951334 --- /dev/null +++ b/shell/ash_test/ash-vars/var_bash_repl_unterminated.tests @@ -0,0 +1,2 @@ +a=b-c +echo ${a/-*}/d diff --git a/shell/hush_test/hush-vars/var_bash_repl_unterminated.right b/shell/hush_test/hush-vars/var_bash_repl_unterminated.right new file mode 100644 index 0000000..5bff3a6 --- /dev/null +++ b/shell/hush_test/hush-vars/var_bash_repl_unterminated.right @@ -0,0 +1 @@ +b/d diff --git a/shell/hush_test/hush-vars/var_bash_repl_unterminated.tests b/shell/hush_test/hush-vars/var_bash_repl_unterminated.tests new file mode 100755 index 0000000..c951334 --- /dev/null +++ b/shell/hush_test/hush-vars/var_bash_repl_unterminated.tests @@ -0,0 +1,2 @@ +a=b-c +echo ${a/-*}/d |