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Fri, 21 Aug 2026 19:41:15 +0000 (GMT) Received: from [9.111.132.173] (unknown [9.111.132.173]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 21 Aug 2026 19:41:15 +0000 (GMT) Message-ID: <2324ecf7-212d-4127-928f-2f801a91f9c9@linux.ibm.com> Date: Fri, 21 Aug 2026 21:41:16 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Jens Remus Subject: Re: [RFC PATCH v1 10/25] unwind_user/eh_frame: Detect .eh_frame_hdr sections in executables To: sashiko-reviews@lists.linux.dev, Josh Poimboeuf , Steven Rostedt Cc: Alexander Gordeev , linux-trace-kernel@vger.kernel.org, Christian Borntraeger , linux-s390@vger.kernel.org, Heiko Carstens , Vasily Gorbik References: <20260818144954.2320378-1-jremus@linux.ibm.com> <20260818144954.2320378-11-jremus@linux.ibm.com> <20260818151823.18F161F000E9@smtp.kernel.org> Content-Language: en-US Organization: IBM Deutschland Research & Development GmbH In-Reply-To: <20260818151823.18F161F000E9@smtp.kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=AdqB2XXG c=1 sm=1 tr=0 ts=6a88a9e1 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=LFt20mCCc4CE-LtB3JUA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: WBmAbrGhqh1Q4WOWoagr8c93-05RzzTf X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODIxMDE1NSBTYWx0ZWRfX7yHkNY7vh88Q vZnMFhgRecWHcpxF8xtpbqhnTyOLJryYMaOyuUuyv/pTEsBXU8/tpmGfyL+S4g5EazR54+c2E+M M8CMxyxhVjEycqUoFMpxcO+iaScMuc1OD3knSCmVYuwyYQOTYmRbE+9cmfS7gm5cWBylIl4f1eA PRt2umcqJ73GvYkeKarOvYJC7HpOY7VefBHomyEwLZPazEr+MMcaXqBvHhDxwNqy3qu5PTRZoXb oHNW5FHKI11t9ZVjXqsCcuVZM41taBPrakYjFvzGpjQo8gS+lxNqOuuT+0D4as5zRNw6AWkYM22 XvIkLu0FGPHEbmR8J/HO0CdA7K8uNWTiR2T0cXnlX4El5uZUBmVaNCi5Gz9hcpumWpzmgh+HOE9 9DrR2sv+ZXeMU4JVKq0ZrAulTxGOGQB1zG1x+QGlsrhKSWvSEwftNETIjJKevswpdSXRo7/mz5p u6gMDHAX3GJTC9knZyQ== X-Proofpoint-Spam-Info: AW1haW4tMjYwODIxMDE1NSBTYWx0ZWRfX1pQmm9ypW916 ifswf7l+3mwZqmhBPEbgS0cx7VtYyJvcBkw4PolHvpA/cMqtbsS2/bo3L3HLtfvFb0xTjuxhaxN NbgQ5++OvqMxxlV4IPKv6pnwlj8Emm4= X-Proofpoint-ORIG-GUID: WBmAbrGhqh1Q4WOWoagr8c93-05RzzTf X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-21_06,2026-08-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 priorityscore=1501 suspectscore=0 malwarescore=0 impostorscore=0 adultscore=0 bulkscore=0 lowpriorityscore=0 phishscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608210155 On 8/18/2026 5:18 PM, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: > - [High] Missing duplication of eh_frame_mt during fork() leaves child processes without stack unwind capability. This is resolved by subsequent patch "unwind_user/eh_frame: Duplicate registered .eh_frame[_hdr] section data on clone/fork". > - [Medium] Executable segments with a trailing BSS section silently fail .eh_frame_hdr registration. Josh, Steven, any thoughts? >> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c >> +static void elf_add_eh_frame(const struct elf_phdr *text, >> + const struct elf_phdr *eh_frame, >> + unsigned long base_addr) >> +{ >> + unsigned long eh_frame_start, eh_frame_end, >> + text_start, text_end; >> + >> + eh_frame_start = base_addr + eh_frame->p_vaddr; >> + eh_frame_end = eh_frame_start + eh_frame->p_memsz; >> + >> + text_start = base_addr + text->p_vaddr; >> + text_end = text_start + text->p_memsz; > > [Severity: Medium] > Will this silently fail to register .eh_frame_hdr for segments with a > trailing BSS section? > > When an ELF executable segment has p_memsz > p_filesz crossing a page > boundary, the loader maps the file-backed portion and creates a separate > anonymous VMA for the BSS. > > Because text_end is calculated using p_memsz, it may extend beyond the > file-backed VMA boundary. When this is passed to eh_frame_add_section(), > it uses vma_lookup() and checks if the entire segment resides in a single > VMA: > > kernel/unwind/eh_frame.c:eh_frame_add_section() { > ... > if (!text_vma || > !(text_vma->vm_flags & VM_EXEC) || > text_end > text_vma->vm_end) { > return -EINVAL; > ... > } > > Since the file-backed VMA ends before text_end in this scenario, won't the > text_end > text_vma->vm_end check fail and terminate registration? > >> + >> + /* Ignore return value, eh_frame[_hdr] section isn't critical */ >> + eh_frame_add_section(eh_frame_start, eh_frame_end, text_start, text_end); >> +} > Thanks and regards, Jens -- Jens Remus Linux on Z Development (D3303) jremus@de.ibm.com / jremus@linux.ibm.com IBM Deutschland Research & Development GmbH; Vorsitzender des Aufsichtsrats: Wolfgang Wendt; Geschäftsführung: David Faller; Sitz der Gesellschaft: Ehningen; Registergericht: Amtsgericht Stuttgart, HRB 243294 IBM Data Privacy Statement: https://www.ibm.com/privacy/