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Subject[PATCH v7 10/10] vsprintf: Limit the length of inlined error messages
Date
The inlined error messages must be used carefully because
they need to fit into the given buffer.

Handle them using a custom wrapper that makes people aware
of the problem. Also define a reasonable hard limit to
avoid a completely insane usage.

Suggested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
---
lib/vsprintf.c | 39 +++++++++++++++++++++++++++------------
1 file changed, 27 insertions(+), 12 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 4e5666035b74..1f367f3a7e2b 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -612,6 +612,21 @@ static char *string_nocheck(char *buf, char *end, const char *s,
return widen_string(buf, len, end, spec);
}

+/* Be careful: error messages must fit into the given buffer. */
+static char *error_string(char *buf, char *end, const char *s,
+ struct printf_spec spec)
+{
+ /*
+ * Hard limit to avoid a completely insane messages. It actually
+ * works pretty well because most error messages are in
+ * the many pointer format modifiers.
+ */
+ if (spec.precision == -1)
+ spec.precision = 2 * sizeof(void *);
+
+ return string_nocheck(buf, end, s, spec);
+}
+
/*
* This is not a fool-proof test. 99% of the time that this will fault is
* due to a bad pointer, not one that crosses into bad memory. Just test
@@ -638,7 +653,7 @@ static int check_pointer(char **buf, char *end, const void *ptr,

err_msg = check_pointer_msg(ptr);
if (err_msg) {
- *buf = string_nocheck(*buf, end, err_msg, spec);
+ *buf = error_string(*buf, end, err_msg, spec);
return -EFAULT;
}

@@ -741,7 +756,7 @@ static char *ptr_to_id(char *buf, char *end, const void *ptr,
if (static_branch_unlikely(&not_filled_random_ptr_key)) {
spec.field_width = 2 * sizeof(ptr);
/* string length must be less than default_width */
- return string_nocheck(buf, end, str, spec);
+ return error_string(buf, end, str, spec);
}

#ifdef CONFIG_64BIT
@@ -777,7 +792,7 @@ char *restricted_pointer(char *buf, char *end, const void *ptr,
if (in_irq() || in_serving_softirq() || in_nmi()) {
if (spec.field_width == -1)
spec.field_width = 2 * sizeof(ptr);
- return string_nocheck(buf, end, "pK-error", spec);
+ return error_string(buf, end, "pK-error", spec);
}

/*
@@ -1511,12 +1526,12 @@ char *ip_addr_string(char *buf, char *end, const void *ptr,
case AF_INET6:
return ip6_addr_string_sa(buf, end, &sa->v6, spec, fmt);
default:
- return string_nocheck(buf, end, "(einval)", spec);
+ return error_string(buf, end, "(einval)", spec);
}}
}

err_fmt_msg = fmt[0] == 'i' ? "(%pi?)" : "(%pI?)";
- return string_nocheck(buf, end, err_fmt_msg, spec);
+ return error_string(buf, end, err_fmt_msg, spec);
}

static noinline_for_stack
@@ -1653,7 +1668,7 @@ char *netdev_bits(char *buf, char *end, const void *addr,
size = sizeof(netdev_features_t);
break;
default:
- return string_nocheck(buf, end, "(%pN?)", spec);
+ return error_string(buf, end, "(%pN?)", spec);
}

return special_hex_number(buf, end, num, size);
@@ -1765,7 +1780,7 @@ char *time_and_date(char *buf, char *end, void *ptr, struct printf_spec spec,
case 'R':
return rtc_str(buf, end, (const struct rtc_time *)ptr, spec, fmt);
default:
- return string_nocheck(buf, end, "(%ptR?)", spec);
+ return error_string(buf, end, "(%ptR?)", spec);
}
}

@@ -1774,7 +1789,7 @@ char *clock(char *buf, char *end, struct clk *clk, struct printf_spec spec,
const char *fmt)
{
if (!IS_ENABLED(CONFIG_HAVE_CLK))
- return string_nocheck(buf, end, "(%pC?)", spec);
+ return error_string(buf, end, "(%pC?)", spec);

if (check_pointer(&buf, end, clk, spec))
return buf;
@@ -1785,7 +1800,7 @@ char *clock(char *buf, char *end, struct clk *clk, struct printf_spec spec,
#ifdef CONFIG_COMMON_CLK
return string(buf, end, __clk_get_name(clk), spec);
#else
- return string_nocheck(buf, end, "(%pC?)", spec);
+ return error_string(buf, end, "(%pC?)", spec);
#endif
}
}
@@ -1843,7 +1858,7 @@ char *flags_string(char *buf, char *end, void *flags_ptr,
names = gfpflag_names;
break;
default:
- return string_nocheck(buf, end, "(%pG?)", spec);
+ return error_string(buf, end, "(%pG?)", spec);
}

return format_flags(buf, end, flags, names);
@@ -1899,7 +1914,7 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
str_spec.field_width = -1;

if (!IS_ENABLED(CONFIG_OF))
- return string_nocheck(buf, end, "(%pOF?)", spec);
+ return error_string(buf, end, "(%pOF?)", spec);

if (check_pointer(&buf, end, dn, spec))
return buf;
@@ -1978,7 +1993,7 @@ static char *kobject_string(char *buf, char *end, void *ptr,
return device_node_string(buf, end, ptr, spec, fmt + 1);
}

- return string_nocheck(buf, end, "(%pO?)", spec);
+ return error_string(buf, end, "(%pO?)", spec);
}

/*
--
2.16.4
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