Description: [CVE-2021-26937] Fix out of bounds array access Author: Michael Schröder Bug-Debian: https://bugs.debian.org/982435 Bug: https://savannah.gnu.org/bugs/?60030 Bug: https://lists.gnu.org/archive/html/screen-devel/2021-02/msg00000.html Bug-OSS-Security: https://www.openwall.com/lists/oss-security/2021/02/09/3 Origin: https://lists.gnu.org/archive/html/screen-devel/2021-02/msg00010.html --- a/encoding.c +++ b/encoding.c @@ -43,7 +43,7 @@ # ifdef UTF8 static int recode_char __P((int, int, int)); static int recode_char_to_encoding __P((int, int)); -static void comb_tofront __P((int, int)); +static void comb_tofront __P((int)); # ifdef DW_CHARS static int recode_char_dw __P((int, int *, int, int)); static int recode_char_dw_to_encoding __P((int, int *, int)); @@ -1263,6 +1263,8 @@ {0x30000, 0x3FFFD}, }; + if (c >= 0xdf00 && c <= 0xdfff) + return 1; /* dw combining sequence */ return ((bisearch(c, wide, sizeof(wide) / sizeof(struct interval) - 1)) || (cjkwidth && bisearch(c, ambiguous, @@ -1330,11 +1332,12 @@ } static void -comb_tofront(root, i) -int root, i; +comb_tofront(i) +int i; { for (;;) { + int root = i >= 0x700 ? 0x801 : 0x800; debug1("bring to front: %x\n", i); combchars[combchars[i]->prev]->next = combchars[i]->next; combchars[combchars[i]->next]->prev = combchars[i]->prev; @@ -1396,9 +1399,9 @@ { /* full, recycle old entry */ if (c1 >= 0xd800 && c1 < 0xe000) - comb_tofront(root, c1 - 0xd800); + comb_tofront(c1 - 0xd800); i = combchars[root]->prev; - if (c1 == i + 0xd800) + if (i == 0x800 || i == 0x801 || c1 == i + 0xd800) { /* completely full, can't recycle */ debug("utf8_handle_comp: completely full!\n"); @@ -1422,7 +1425,7 @@ mc->font = (i >> 8) + 0xd8; mc->fontx = 0; debug3("combinig char %x %x -> %x\n", c1, c, i + 0xd800); - comb_tofront(root, i); + comb_tofront(i); } #else /* !UTF8 */