From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 538643858409; Mon, 21 Feb 2022 11:49:58 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 538643858409 From: "cvs-commit at gcc dot gnu.org" To: gdb-prs@sourceware.org Subject: [Bug symtab/28900] GDB crash on loading symbols form openbios binary Date: Mon, 21 Feb 2022 11:49:58 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gdb X-Bugzilla-Component: symtab X-Bugzilla-Version: 11.2 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: cvs-commit at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at sourceware dot org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://sourceware.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: gdb-prs@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-prs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 21 Feb 2022 11:49:58 -0000 https://sourceware.org/bugzilla/show_bug.cgi?id=3D28900 --- Comment #10 from cvs-commit at gcc dot gnu.org --- The master branch has been updated by Andrew Burgess : https://sourceware.org/git/gitweb.cgi?p=3Dbinutils-gdb.git;h=3D336125713fcf= 9b43960a57724fa39a319036ba38 commit 336125713fcf9b43960a57724fa39a319036ba38 Author: Andrew Burgess Date: Sat Feb 19 13:09:34 2022 +0000 gdb: avoid nullptr access in dbxread.c from read_dbx_symtab This fixes a GDB crash reported in bug pr/28900, related to reading in some stabs debug information. In this commit my goal is to stop GDB crashing. I am not trying to ensure that GDB makes the best possible use of the available stabs debug information. At this point I consider stabs a legacy debug format, with only limited support in GDB. So, the problem appears to be that, when reading in the stabs data, we need to find a N_SO entry, this is the entry that defines the start of a compilation unit (or at least the location of a corresponding source file). It is while handling an N_SO that GDB creates a psymtab to hold the incoming debug information (symbols, etc). The problem we hit in the bug is that we encounter some symbol information (an N_PC entry) outside of an N_SO entry - that is we find some symbol information that is not associated with any source file. We already have some protection for this case, look (in read_dbx_symtab) at the handling of N_PC entries of type 'F' and 'f', if we have no psymtab (the pst variable is nullptr) then we issue a complaint. However, for whatever reason, in both 'f' and 'F' handling, there is one place where we assume that the pst variable (the psymtab) is not nullptr. This is a mistake. In this commit, I guard these two locations (in 'f' and 'F' handling) so we no longer assume pst is not nullptr. While I was at it, I audited all the other uses of pst in read_dbx_symtab, and in every potentially dangerous case I added a nullptr check, and issue a suitable complaint if pst is found to be nullptr. It might well be true that we could/should do something smarter if we see a debug symbol outside of an N_SO entry, and if anyone wanted to do that work, they're welcome too. But this commit is just about preventing the nullptr access, and the subsequent GDB crash. I don't have any tests for this change, I have no idea how to generate weird stabs data for testing. The original binary from the bug report now loads just fine without GDB crashing. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=3D28900 --=20 You are receiving this mail because: You are on the CC list for the bug.=