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Peter Anvin" , Namhyung Kim , Andrii Nakryiko , Kees Cook , Sam James , Fangrui Song Subject: [RFC PATCH v2 14/24] unwind_user/eh_frame: Add .eh_frame[_hdr] validation option Date: Fri, 21 Aug 2026 21:52:49 +0200 Message-ID: <20260821195259.2688377-15-jremus@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260821195259.2688377-1-jremus@linux.ibm.com> References: <20260821195259.2688377-1-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-Authority-Analysis: v=2.4 cv=AdqB2XXG c=1 sm=1 tr=0 ts=6a88acaa cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=rU79QueooZ11dTUg0tsA:9 X-Proofpoint-GUID: V0QbgjbecwJnbO6dU4IgQ-bBO3sGdUfh X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODIxMDE1NSBTYWx0ZWRfX1iVigc/iW8LB zeqq4vE+GPJLSxItxBmu3VRnL/3oRRr8kjlci1KHJadHGRC8H43mpt1CqviFREy3nVAJODZ6sS8 h+ZaYSwA7HyQY9krH8TKU5pq6G7v4ziooiCBkfXjD+zXyxo+S+K4njorH6qNu+5bVD3683qrsPR BWd5mxzfiPbDbSmJfz9UjhgnFZsCzPH7F3DITljFiBBDbMSey+LGv1iqnXccg+SS3r4i9KKdgpN dqcOWVMILcDMfHF08nP3KyuF21Yw0S/EkuCa0vVmQv3KpzIi+8muccF18SyIoKLnXJtc5u936dT vjjbdCKvAqHIHue1ISrIK+CjZwy4iixTucHK0wJixY0F9qSqNPAJJCHeg7cqJ+Wl8MZ4k2e6nol F9dsWzGAxRX7Ol6nbVyVwIQMZxIUQrNs1j0cQFMaSOjD40K7mb4JO30O4HkxVWKJPvgPql0mf1Q g0JTqY8RxDnAiAAA0gg== X-Proofpoint-Spam-Info: AW1haW4tMjYwODIxMDE1NSBTYWx0ZWRfX0mQVwO7Z4iLA sNZ6cUUHh4dcWQyiCHC5GHj8vpxe1LxlTshbbBebiyoUro73YJU9uvDE8r1LxykSUrg9HAsDj2i uyESaMo4IaSG23qdrih51d/Z6lyDL+w= X-Proofpoint-ORIG-GUID: lW3CGmU-Qqxb1m_pLlfWazP5XlGeBG4t 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 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. Changes in RFC v2: - Fix compile error. (Sashiko AI) - Correct loop counter type to prevent infinite loop. (Sashiko AI) arch/Kconfig | 22 +++++++++ kernel/unwind/eh_frame.c | 90 ++++++++++++++++++++++++++++++++++ kernel/unwind/eh_frame_debug.h | 4 ++ 3 files changed, 116 insertions(+) diff --git a/arch/Kconfig b/arch/Kconfig index ea969811f798..c06e5010a88a 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 entire .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 96237a96d263..b0be56e31508 100644 --- a/kernel/unwind/eh_frame.c +++ b/kernel/unwind/eh_frame.c @@ -1216,6 +1216,92 @@ 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 long i; + + 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, &cur, + sec->binary_search_table_end, + table_enc, &func_addr); + if (ret) { + dbg_sec_ehfh(cur, "table[%lu]: failed to read function start address\n", i); + return ret; + } + if (i && func_addr <= prev_func_addr) { + dbg_sec(".eh_frame_hdr: table[%lu]: not sorted\n", i); + return -EINVAL; + } + prev_func_addr = func_addr; + + /* Read FDE address from table */ + ret = read_encoded_pointer(sec, &cur, + sec->binary_search_table_end, + table_enc, &fde_addr); + if (ret) { + dbg_sec_ehfh(cur, "table[%lu]: failed to read FDE pointer\n", i); + return ret; + } + if (fde_addr < sec->eh_frame_start) { + dbg_sec(".eh_frame_hdr: table[%lu]: invalid FDE address\n", i); + return -EINVAL; + } + } + + ret = __read_fde(sec, fde_addr, &fde); + if (ret) { + dbg_sec(".eh_frame_hdr: table[%lu]: 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[%lu]: 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); @@ -1351,6 +1437,10 @@ 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