The patch titled
Subject: lib/vsprintf.c: fix potential NULL deref in hex_string
has been added to the -mm tree. Its filename is
lib-vsprintfc-fix-potential-null-deref-in-hex_string.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-vsprintfc-fix-potential-null-deref-in-hex_string.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-vsprintfc-fix-potential-null-deref-in-hex_string.patch
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From: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Subject: lib/vsprintf.c: fix potential NULL deref in hex_string
The helper hex_string() is broken in two ways. First, it doesn't
increment buf regardless of whether there is room to print, so callers
such as kasprintf() that try to probe the correct storage to allocate will
get a too small return value. But even worse, kasprintf() (and likely
anyone else trying to find the size of the result) pass NULL for buf and 0
for size, so we also have end == NULL. But this means that the end-1 in
hex_string() is (char*)-1, so buf < end-1 is true and we get a NULL
pointer deref. I double-checked this with a trivial kernel module that
just did a kasprintf(GFP_KERNEL, "%14ph", "CrashBoomBang").
Nobody seems to be using %ph with kasprintf, but we might as well fix it
before it hits someone.
Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Acked-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/vsprintf.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff -puN lib/vsprintf.c~lib-vsprintfc-fix-potential-null-deref-in-hex_string lib/vsprintf.c
--- a/lib/vsprintf.c~lib-vsprintfc-fix-potential-null-deref-in-hex_string
+++ a/lib/vsprintf.c
@@ -777,11 +777,19 @@ char *hex_string(char *buf, char *end, u
if (spec.field_width > 0)
len = min_t(int, spec.field_width, 64);
- for (i = 0; i < len && buf < end - 1; i++) {
- buf = hex_byte_pack(buf, addr[i]);
+ for (i = 0; i < len; ++i) {
+ if (buf < end)
+ *buf = hex_asc_hi(addr[i]);
+ ++buf;
+ if (buf < end)
+ *buf = hex_asc_lo(addr[i]);
+ ++buf;
- if (buf < end && separator && i != len - 1)
- *buf++ = separator;
+ if (separator && i != len - 1) {
+ if (buf < end)
+ *buf = separator;
+ ++buf;
+ }
}
return buf;
_
Patches currently in -mm which might be from linux@xxxxxxxxxxxxxxxxxx are
origin.patch
include-linux-remove-empty-conditionals.patch
lib-vsprintfc-eliminate-some-branches.patch
lib-vsprintfc-reduce-stack-use-in-number.patch
lib-vsprintfc-eliminate-duplicate-hex-string-array.patch
lib-vsprintfc-another-small-hack.patch
lib-vsprintfc-fix-potential-null-deref-in-hex_string.patch
lib-string_helpersc-refactor-string_escape_mem.patch
lib-string_helpersc-change-semantics-of-string_escape_mem.patch
linux-bitmaph-improve-bitmap_lastfirst_word_mask.patch
lib-find__bit-reimplementation.patch
lib-find__bit-reimplementation-fix.patch
lib-move-find_last_bit-to-lib-find_next_bitc.patch
lib-rename-lib-find_next_bitc-to-lib-find_bitc.patch
binfmt_misc-simplify-entry_status.patch
binfmt_misc-simplify-entry_status-fix.patch
rtc-mc13xxx-fix-obfuscated-and-wrong-format-string.patch
lib-lz4-pull-out-constant-tables.patch
linux-next.patch
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