[PATCH v6 1/4] string_helpers: Escape double quotes in escape_special

From: Chris Down
Date: Tue May 18 2021 - 08:00:42 EST


>From an abstract point of view, escape_special's counterpart,
unescape_special, already handles the unescaping of blackslashed double
quote sequences.

As a more practical example, printk indexing is an example case where
this is already practically useful. Compare an example with
`ESCAPE_SPECIAL | ESCAPE_SPACE`, with quotes not escaped:

[root@ktst ~]# grep drivers/pci/pci-stub.c:69 /sys/kernel/debug/printk/index/vmlinux
<4> drivers/pci/pci-stub.c:69 pci_stub_init "pci-stub: invalid ID string "%s"\n"

...and the same after this patch:

[root@ktst ~]# grep drivers/pci/pci-stub.c:69 /sys/kernel/debug/printk/index/vmlinux
<4> drivers/pci/pci-stub.c:69 pci_stub_init "pci-stub: invalid ID string \"%s\"\n"

One can of course, alternatively, use ESCAPE_APPEND with a quote in
@only, but without this patch quotes are coerced into hex or octal which
can hurt readability quite significantly.

A new ESCAPE_QUOTE/ESCAPE_PRINTK option is also possible, but it seems
reasonable to use the simplest strategy first, since this is already
decoded properly.

Signed-off-by: Chris Down <chris@xxxxxxxxxxxxxx>
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
---
lib/string_helpers.c | 4 ++++
lib/test-string_helpers.c | 14 +++++++-------
2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index 5a35c7e16e96..3806a52ce697 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -361,6 +361,9 @@ static bool escape_special(unsigned char c, char **dst, char *end)
case '\e':
to = 'e';
break;
+ case '"':
+ to = '"';
+ break;
default:
return false;
}
@@ -474,6 +477,7 @@ static bool escape_hex(unsigned char c, char **dst, char *end)
* '\t' - horizontal tab
* '\v' - vertical tab
* %ESCAPE_SPECIAL:
+ * '\"' - double quote
* '\\' - backslash
* '\a' - alert (BEL)
* '\e' - escape
diff --git a/lib/test-string_helpers.c b/lib/test-string_helpers.c
index 2185d71704f0..437d8e6b7cb1 100644
--- a/lib/test-string_helpers.c
+++ b/lib/test-string_helpers.c
@@ -140,13 +140,13 @@ static const struct test_string_2 escape0[] __initconst = {{
},{
.in = "\\h\\\"\a\e\\",
.s1 = {{
- .out = "\\\\h\\\\\"\\a\\e\\\\",
+ .out = "\\\\h\\\\\\\"\\a\\e\\\\",
.flags = ESCAPE_SPECIAL,
},{
- .out = "\\\\\\150\\\\\\042\\a\\e\\\\",
+ .out = "\\\\\\150\\\\\\\"\\a\\e\\\\",
.flags = ESCAPE_SPECIAL | ESCAPE_OCTAL,
},{
- .out = "\\\\\\x68\\\\\\x22\\a\\e\\\\",
+ .out = "\\\\\\x68\\\\\\\"\\a\\e\\\\",
.flags = ESCAPE_SPECIAL | ESCAPE_HEX,
},{
/* terminator */
@@ -157,10 +157,10 @@ static const struct test_string_2 escape0[] __initconst = {{
.out = "\eb \\C\007\"\x90\\r]",
.flags = ESCAPE_SPACE,
},{
- .out = "\\eb \\\\C\\a\"\x90\r]",
+ .out = "\\eb \\\\C\\a\\\"\x90\r]",
.flags = ESCAPE_SPECIAL,
},{
- .out = "\\eb \\\\C\\a\"\x90\\r]",
+ .out = "\\eb \\\\C\\a\\\"\x90\\r]",
.flags = ESCAPE_SPACE | ESCAPE_SPECIAL,
},{
.out = "\\033\\142\\040\\134\\103\\007\\042\\220\\015\\135",
@@ -169,10 +169,10 @@ static const struct test_string_2 escape0[] __initconst = {{
.out = "\\033\\142\\040\\134\\103\\007\\042\\220\\r\\135",
.flags = ESCAPE_SPACE | ESCAPE_OCTAL,
},{
- .out = "\\e\\142\\040\\\\\\103\\a\\042\\220\\015\\135",
+ .out = "\\e\\142\\040\\\\\\103\\a\\\"\\220\\015\\135",
.flags = ESCAPE_SPECIAL | ESCAPE_OCTAL,
},{
- .out = "\\e\\142\\040\\\\\\103\\a\\042\\220\\r\\135",
+ .out = "\\e\\142\\040\\\\\\103\\a\\\"\\220\\r\\135",
.flags = ESCAPE_SPACE | ESCAPE_SPECIAL | ESCAPE_OCTAL,
},{
.out = "\eb \\C\007\"\x90\r]",
--
2.31.1