From cbfa85811792ca8e96ace40bef0aaaf507e54bcc Mon Sep 17 00:00:00 2001 From: Shahab Vahedi Date: Mon, 6 Jan 2020 15:27:32 +0100 Subject: [PATCH] GDB: Fix the overflow in addr/line_is_displayed() In tui_disasm_window::addr_is_displayed(), there can be situations where "content" is empty. For instance, it can happen when the "content" was not filled in tui_disasm_window::set_contents(), because tui_disassemble() threw an exception. Usually this exception is the result of fetching invalid PC addresses like the ones beyond the end of the program. Having "content.size ()" zero leads to an overflow in this condition check inside tui_disasm_window::addr_is_displayed(): int i = 0; while (i < content.size () - threshold ...) { ... content[i] ... } "threshold" is 2 and there are times that "content.size ()" is 0. This results into an overflow and the loop is entered whereas it should have been skipped. Finally, "content[i]" access leads to a segmentation fault. Same problem applies to tui_source_window::line_is_displayed(). The issue has been discussed at length in bug 25345: https://sourceware.org/bugzilla/show_bug.cgi?id=25345 This commit avoids the segmentation faults with an early check: if (content.size () < SCROLL_THRESHOLD) return false; Moreover, those functions have been overhauled to a leaner code. gdb/ChangeLog: 2020-01-06 Shahab Vahedi * tui/tui-disasm.c (tui_disasm_window::addr_is_displayed): Avoid overflow by an early check of content vs threshold. * tui/tui-source.c (tui_source_window::line_is_displayed): Likewise. --- gdb/ChangeLog | 7 +++++++ gdb/tui/tui-disasm.c | 16 +++++++--------- gdb/tui/tui-source.c | 17 ++++++++--------- 3 files changed, 22 insertions(+), 18 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 69e426e0e62..476712e6cba 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,10 @@ +2020-01-06 Shahab Vahedi + + * tui/tui-disasm.c (tui_disasm_window::addr_is_displayed): Avoid + overflow by an early check of content vs threshold. + * tui/tui-source.c (tui_source_window::line_is_displayed): + Likewise. + 2020-01-06 Eli Zaretskii * NEWS: Mention the recent fix of $_exitsignal on MS-Windows. diff --git a/gdb/tui/tui-disasm.c b/gdb/tui/tui-disasm.c index ebd0ba317f5..98c691f3387 100644 --- a/gdb/tui/tui-disasm.c +++ b/gdb/tui/tui-disasm.c @@ -348,19 +348,17 @@ tui_disasm_window::location_matches_p (struct bp_location *loc, int line_no) bool tui_disasm_window::addr_is_displayed (CORE_ADDR addr) const { - bool is_displayed = false; - int threshold = SCROLL_THRESHOLD; + if (content.size () < SCROLL_THRESHOLD) + return false; - int i = 0; - while (i < content.size () - threshold && !is_displayed) + for (size_t i = 0; i < content.size () - SCROLL_THRESHOLD; ++i) { - is_displayed - = (content[i].line_or_addr.loa == LOA_ADDRESS - && content[i].line_or_addr.u.addr == addr); - i++; + if (content[i].line_or_addr.loa == LOA_ADDRESS + && content[i].line_or_addr.u.addr == addr) + return true; } - return is_displayed; + return false; } void diff --git a/gdb/tui/tui-source.c b/gdb/tui/tui-source.c index e028b724d23..1503cd4c636 100644 --- a/gdb/tui/tui-source.c +++ b/gdb/tui/tui-source.c @@ -174,18 +174,17 @@ tui_source_window::location_matches_p (struct bp_location *loc, int line_no) bool tui_source_window::line_is_displayed (int line) const { - bool is_displayed = false; - int threshold = SCROLL_THRESHOLD; - int i = 0; - while (i < content.size () - threshold && !is_displayed) + if (content.size () < SCROLL_THRESHOLD) + return false; + + for (size_t i = 0; i < content.size () - SCROLL_THRESHOLD; ++i) { - is_displayed - = (content[i].line_or_addr.loa == LOA_LINE - && content[i].line_or_addr.u.line_no == line); - i++; + if (content[i].line_or_addr.loa == LOA_LINE + && content[i].line_or_addr.u.line_no == line) + return true; } - return is_displayed; + return false; } void -- 2.30.2