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string_helpers: Escape double quotes in escape_special 

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.

I've checked uses of ESCAPE_SPECIAL and %pE across the codebase, and I'm
pretty confident that this shouldn't affect any stable interfaces.

Signed-off-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/af144c5b75e41ce417386253ba2694456bc04118.1623775748.git.chris@chrisdown.name
This commit is contained in:
Chris Down 2021-06-15 17:52:45 +01:00 committed by Petr Mladek
parent e73f0f0ee7
commit 91027d0a7a
2 changed files with 11 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
lib/string_helpers.c
View File

@ -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

14
lib/test-string_helpers.c
View File

@ -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]",