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Peter Anvin" , Namhyung Kim , Andrii Nakryiko , Kees Cook , Sam James Subject: [RFC PATCH v1 14/25] unwind_user/eh_frame: Add .eh_frame[_hdr] validation option Date: Tue, 18 Aug 2026 16:49:43 +0200 Message-ID: <20260818144954.2320378-15-jremus@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260818144954.2320378-1-jremus@linux.ibm.com> References: <20260818144954.2320378-1-jremus@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODE4MDEwNyBTYWx0ZWRfXxdiWQUmGpLmF Es+Ul7Ut05h3BxA9bQWZ+ESdQm7nnAUvuFNQv0wmGgK9pqVM+Yezu0ECEpmqBeMnexGwnrDRCCr 0NaLChYxner/I5kHidyszNRcuTtL2Yz5wrLY0v8DEGghMSgW9qL1ETzkIrrKdUSkfWHrmuwb3V1 mWvnQy8qb5hFBdVFM+s6aENB63MDq7hOxH5OhsUROfLAIt3tp0fBGqd8o51r6M5zR90MZjVUoCH +UBnMSykVJExnv0nHIven2rAe19NAx8MXUO4FrGdEW7G3q5kAHNO3q+dh8m5u3n03EA2oG/pawD JWs89I/elbQ8PAktF0FgJTcFtktVvKf73v+8HdDaEQylOPFEk1FH1hmqmR8mBggIEk4jT5LT3AI KOif6LQ/W1iYnvRBkW5TPshvCaoHE69eiZN23cdoZcH2lUcDwtllyVrAtzZUkosyjlHA5h7AegS dpfnllP9xJOP1J1uU/g== X-Proofpoint-Spam-Info: AW1haW4tMjYwODE4MDEwNyBTYWx0ZWRfX0CGjpXFcH5yb L38p9xrKWEazqqMkubPUNXxYBEszDe0D4+SCBCSCgOuKMv6ad2BlbbY1SCbryH866lza5C+MZ8+ 8W//oX++KwStq54LTtT+raBdp+cx09U= X-Authority-Analysis: v=2.4 cv=JKkLdcKb c=1 sm=1 tr=0 ts=6a84711f cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=rU79QueooZ11dTUg0tsA:9 X-Proofpoint-ORIG-GUID: EMpV_nXwfK9MoGn3zsJoPwCjhCYNKNRx X-Proofpoint-GUID: rzNcgYVZdpiVLSneaMjv_Zb9H1zW4w4i 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=2026-08-18_02,2026-08-18_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 bulkscore=0 malwarescore=0 priorityscore=1501 lowpriorityscore=0 clxscore=1015 adultscore=0 impostorscore=0 spamscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608180107 Add a debug feature to validate all .eh_frame[_hdr] sections when first loading the file rather than on demand. Signed-off-by: Jens Remus --- Notes (jremus): FIXME: dbg*() with UACCESS enabled. arch/Kconfig | 22 ++++++++ kernel/unwind/eh_frame.c | 93 ++++++++++++++++++++++++++++++++++ kernel/unwind/eh_frame_debug.h | 4 ++ 3 files changed, 119 insertions(+) diff --git a/arch/Kconfig b/arch/Kconfig index ea969811f798..30d9e876f28a 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -490,6 +490,28 @@ config HAVE_UNWIND_USER_EH_FRAME bool select UNWIND_USER +config EH_FRAME_VALIDATION + bool "Enable .eh_frame[_hdr] section debugging" + depends on HAVE_UNWIND_USER_EH_FRAME + depends on DYNAMIC_DEBUG + help + When adding an .eh_frame_hdr section for a test, validate the + entire section and its referenced entrire .eh_frame section + immediately rather than on demand. + + This is a debug feature which is helpful for rooting out + .eh_frame[_hdr] section issues. If the .eh_frame[_hdr] + section is corrupt, it will fail to load immediately, with + more information provided in dynamic printks. + + This has a significant page cache footprint due to its reading + of the entire .eh_frame[_hdr] sections for every loaded executable + and shared library. Also, it's done for all processes, even those + which don't get stack traced by the kernel. Not recommended for + general use. + + If unsure, say N. + config HAVE_UNWIND_USER_FP bool select UNWIND_USER diff --git a/kernel/unwind/eh_frame.c b/kernel/unwind/eh_frame.c index 46ffb535ca53..c9161229196c 100644 --- a/kernel/unwind/eh_frame.c +++ b/kernel/unwind/eh_frame.c @@ -1163,6 +1163,95 @@ int eh_frame_find(unsigned long ip, struct unwind_user_frame *frame) return ret; } +#ifdef CONFIG_EH_FRAME_VALIDATION + +static int eh_frame_validate_section(struct eh_frame_section *sec) +{ + void __user *table_start_ptr; + unsigned long table_size; + u8 table_enc; + int entry_size; + unsigned long prev_func_addr; + unsigned int i; + + if (!sec->has_binary_search_table) + return 0; + + if (!sec->fde_count) { + dbg_sec(".eh_frame_hdr: invalid FDE count\n"); + return -EINVAL; + } + + table_enc = sec->binary_search_table_enc; + entry_size = 2 * encoded_pointer_size(table_enc); + if (!entry_size) { + dbg_sec(".eh_frame_hdr: invalid binary search table entry size\n"); + return -EINVAL; + } + table_start_ptr = (void __user *)sec->binary_search_table_start; + table_size = sec->binary_search_table_end - sec->binary_search_table_start; + + for (i = 0; i < sec->fde_count; i++) { + struct eh_frame_fde fde; + unsigned long cur; + unsigned long func_addr, fde_addr; + int ret; + + cur = sec->binary_search_table_start + i * entry_size; + + scoped_user_read_access_size(table_start_ptr, table_size, Efault) { + /* Read function start address from table */ + ret = read_encoded_pointer(sec, NULL, &cur, + sec->binary_search_table_end, + table_enc, &func_addr); + if (ret) { + dbg_sec_ehfh(cur, "table[%u]: failed to read function start address\n", i); + return ret; + } + if (i && func_addr <= prev_func_addr) { + dbg_sec(".eh_frame_hdr: table[%u]: not sorted\n", i); + return -EINVAL; + } + prev_func_addr = func_addr; + + /* Read FDE address from table */ + ret = read_encoded_pointer(sec, NULL, &cur, + sec->binary_search_table_end, + table_enc, &fde_addr); + if (ret) { + dbg_sec_ehfh(cur, "table[%u]: failed to read FDE pointer\n", i); + return ret; + } + if (fde_addr < sec->eh_frame_start) { + dbg_sec(".eh_frame_hdr: table[%u]: invalid FDE address\n", i); + return -EINVAL; + } + } + + ret = __read_fde(sec, fde_addr, &fde); + if (ret) { + dbg_sec(".eh_frame_hdr: table[%u]: failed to read FDE at .eh_frame+%#lx\n", + i, fde_addr - sec->eh_frame_start); + return ret; + } + if (func_addr != fde.func_addr) { + dbg_sec(".eh_frame_hdr: table[%u]: function start address mismatch\n", i); + return -EINVAL; + } + } + + return 0; + +Efault: + return -EFAULT; +} + +#else /* !CONFIG_EH_FRAME_VALIDATION */ + +static int eh_frame_validate_section(struct eh_frame_section *sec) { return 0; } + +#endif /* !CONFIG_EH_FRAME_VALIDATION */ + static void free_section(struct eh_frame_section *sec) { dbg_free(sec); @@ -1299,6 +1388,10 @@ int eh_frame_add_section(unsigned long eh_frame_hdr_start, if (ret) goto err_free; + ret = eh_frame_validate_section(sec); + if (ret) + goto err_free; + ret = mtree_insert_range(eh_frame_mt, sec->text_start, sec->text_end - 1, sec, GFP_KERNEL_ACCOUNT); if (ret) { diff --git a/kernel/unwind/eh_frame_debug.h b/kernel/unwind/eh_frame_debug.h index 40a80861d4d4..bcb2d03ab9ab 100644 --- a/kernel/unwind/eh_frame_debug.h +++ b/kernel/unwind/eh_frame_debug.h @@ -14,6 +14,9 @@ #define dbg_sec(fmt, ...) \ dbg("%s: " fmt, sec->filename, ##__VA_ARGS__) +#define dbg_sec_ehfh(addr, fmt, ...) \ + dbg_sec(".eh_frame_hdr+%#lx: " fmt, ((addr) - sec->eh_frame_hdr_start), ##__VA_ARGS__) + static inline void dbg_init(struct eh_frame_section *sec) { struct mm_struct *mm = current->mm; @@ -47,6 +50,7 @@ static inline void dbg_free(struct eh_frame_section *sec) #define dbg(args...) no_printk(args) #define dbg_sec(args...) no_printk(args) +#define dbg_sec_ehfh(args...) no_printk(args) static inline void dbg_init(struct eh_frame_section *sec) {} static inline void dbg_free(struct eh_frame_section *sec) {} -- 2.53.0