From ed8f6d9cc68fbadb26ee3009a3017b3e3ea63f28 Mon Sep 17 00:00:00 2001 From: Qualys Security Advisory Date: Thu, 1 Jan 1970 00:00:00 +0000 Subject: [PATCH] top: Fix out-of-bounds read/write in show_special(). This patch fixes two problems: 1/ In the switch case 0, if sub_end is at the very end of lin[], the two null-byte writes are off-by-two (a stack-based buffer overflow). Replace this end-of-string "emulation" with an equivalent test on ch (and then goto/break out of the loop). 2/ "sub_end += 2" jumps over the null-byte terminator in lin[] if the line contains a raw (without a tilde) \001-\010 character. Detect such a null-byte terminator and goto/break out of the loop. Note: in the case of a raw \001-\010 character, the character at "sub_end + 1" is never processed (it is skipped/jumped over); this is not a security problem anymore (since 2/ was fixed), so we decided not to change this behavior, for backward-compatibility. --- top/top.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/top/top.c b/top/top.c index 018c8bb7..7ff52e97 100644 --- a/top/top.c +++ b/top/top.c @@ -972,8 +972,6 @@ static void show_special (int interact, const char *glob) { if ('~' == ch) ch = *(sub_end + 1) - '0'; switch (ch) { case 0: // no end delim, captab makes normal - *(sub_end + 1) = '\0'; // extend str end, then fall through - *(sub_end + 2) = '\0'; // ( +1 optimization for usual path ) case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 8: *sub_end = '\0'; @@ -982,6 +980,8 @@ static void show_special (int interact, const char *glob) { rp = scat(rp, tmp, row, sizeof(row)); room -= (sub_end - sub_beg); room += utf8_delta(sub_beg); + if (!ch) goto done_substrings; + if (!*(sub_end + 1)) goto done_substrings; sub_beg = (sub_end += 2); break; default: // nothin' special, just text @@ -989,6 +989,7 @@ static void show_special (int interact, const char *glob) { } if (0 >= room) break; // skip substrings that won't fit } +done_substrings: if (interact) PUTT("%s%s\n", row, Cap_clr_eol); else PUFF("%s%s\n", row, Caps_endline);