The patch titled
Subject: lib/vsprintf.c: eliminate potential race in string()
has been added to the -mm tree. Its filename is
lib-vsprintfc-eliminate-potential-race-in-string.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-vsprintfc-eliminate-potential-race-in-string.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-vsprintfc-eliminate-potential-race-in-string.patch
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------------------------------------------------------
From: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Subject: lib/vsprintf.c: eliminate potential race in string()
If the string corresponding to a %s specifier can change under us, we
might end up copying a \0 byte to the output buffer. There might be
callers who expect the output buffer to contain a genuine C string whose
length is exactly the snprintf return value (assuming truncation hasn't
happened or has been checked for).
We can avoid this by only passing over the source string once, stopping
the first time we meet a nul byte (or when we reach the given precision),
and then letting widen_string() handle left/right space padding.
Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/vsprintf.c | 28 +++++++++-------------------
1 file changed, 9 insertions(+), 19 deletions(-)
diff -puN lib/vsprintf.c~lib-vsprintfc-eliminate-potential-race-in-string lib/vsprintf.c
--- a/lib/vsprintf.c~lib-vsprintfc-eliminate-potential-race-in-string
+++ a/lib/vsprintf.c
@@ -557,32 +557,22 @@ char *widen_string(char *buf, int n, cha
static noinline_for_stack
char *string(char *buf, char *end, const char *s, struct printf_spec spec)
{
- int len, i;
+ int len = 0;
+ size_t lim = spec.precision;
if ((unsigned long)s < PAGE_SIZE)
s = "(null)";
- len = strnlen(s, spec.precision);
-
- if (!(spec.flags & LEFT)) {
- while (len < spec.field_width--) {
- if (buf < end)
- *buf = ' ';
- ++buf;
- }
- }
- for (i = 0; i < len; ++i) {
+ while (lim--) {
+ char c = *s++;
+ if (!c)
+ break;
if (buf < end)
- *buf = *s;
- ++buf; ++s;
- }
- while (len < spec.field_width--) {
- if (buf < end)
- *buf = ' ';
+ *buf = c;
++buf;
+ ++len;
}
-
- return buf;
+ return widen_string(buf, len, end, spec);
}
static noinline_for_stack
_
Patches currently in -mm which might be from linux@xxxxxxxxxxxxxxxxxx are
lib-vsprintfc-pull-out-padding-code-from-dentry_name.patch
lib-vsprintfc-move-string-below-widen_string.patch
lib-vsprintfc-eliminate-potential-race-in-string.patch
lib-vsprintfc-expand-field_width-to-24-bits.patch
lib-vsprintfc-help-gcc-make-number-smaller.patch
lib-vsprintfc-warn-about-too-large-precisions-and-field-widths.patch
lib-test_printfc-dont-bug.patch
lib-test_printfc-check-for-out-of-bound-writes.patch
lib-test_printfc-add-a-few-string-tests.patch
lib-test_printfc-account-for-kvasprintf-tests.patch
lib-test_printfc-add-test-for-large-bitmaps.patch
lib-test_printfc-test-dentry-printing.patch
lib-kasprintfc-add-sanity-check-to-kvasprintf.patch
powerpc-fadump-rename-cpu_online_mask-member-of-struct-fadump_crash_info_header.patch
kernel-cpuc-change-type-of-cpu_possible_bits-and-friends.patch
kernel-cpuc-export-__cpu__mask.patch
drivers-base-cpuc-use-__cpu__mask-directly.patch
kernel-cpuc-eliminate-cpu__mask.patch
kernel-cpuc-make-set_cpu_-static-inlines.patch
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