From 35adf9a4e55e0b0a9d5e313e65ad83681dc32e9a Mon Sep 17 00:00:00 2001 From: Adrian Hunter Date: Fri, 1 Jul 2022 12:44:03 +0300 Subject: modules: Fix corruption of /proc/kallsyms The commit 91fb02f31505 ("module: Move kallsyms support into a separate file") changed from using strlcpy() to using strscpy() which created a buffer overflow. That happened because: 1) an incorrect value was passed as the buffer length 2) strscpy() (unlike strlcpy()) may copy beyond the length of the input string when copying word-by-word. The assumption was that because it was already known that the strings being copied would fit in the space available, it was not necessary to correctly set the buffer length. strscpy() breaks that assumption because although it will not touch bytes beyond the given buffer length it may write bytes beyond the input string length when writing word-by-word. The result of the buffer overflow is to corrupt the symbol type information that follows. e.g. $ sudo cat -v /proc/kallsyms | grep '\^' | head ffffffffc0615000 ^@ rfcomm_session_get [rfcomm] ffffffffc061c060 ^@ session_list [rfcomm] ffffffffc06150d0 ^@ rfcomm_send_frame [rfcomm] ffffffffc0615130 ^@ rfcomm_make_uih [rfcomm] ffffffffc07ed58d ^@ bnep_exit [bnep] ffffffffc07ec000 ^@ bnep_rx_control [bnep] ffffffffc07ec1a0 ^@ bnep_session [bnep] ffffffffc07e7000 ^@ input_leds_event [input_leds] ffffffffc07e9000 ^@ input_leds_handler [input_leds] ffffffffc07e7010 ^@ input_leds_disconnect [input_leds] Notably, the null bytes (represented above by ^@) can confuse tools. Fix by correcting the buffer length. Fixes: 91fb02f31505 ("module: Move kallsyms support into a separate file") Signed-off-by: Adrian Hunter Signed-off-by: Luis Chamberlain --- kernel/module/kallsyms.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c index 3e11523bc6f6..18c23545b984 100644 --- a/kernel/module/kallsyms.c +++ b/kernel/module/kallsyms.c @@ -137,6 +137,7 @@ void layout_symtab(struct module *mod, struct load_info *info) info->symoffs = ALIGN(mod->data_layout.size, symsect->sh_addralign ?: 1); info->stroffs = mod->data_layout.size = info->symoffs + ndst * sizeof(Elf_Sym); mod->data_layout.size += strtab_size; + /* Note add_kallsyms() computes strtab_size as core_typeoffs - stroffs */ info->core_typeoffs = mod->data_layout.size; mod->data_layout.size += ndst * sizeof(char); mod->data_layout.size = strict_align(mod->data_layout.size); @@ -169,6 +170,7 @@ void add_kallsyms(struct module *mod, const struct load_info *info) Elf_Sym *dst; char *s; Elf_Shdr *symsec = &info->sechdrs[info->index.sym]; + unsigned long strtab_size; /* Set up to point into init section. */ mod->kallsyms = (void __rcu *)mod->init_layout.base + @@ -190,19 +192,26 @@ void add_kallsyms(struct module *mod, const struct load_info *info) mod->core_kallsyms.symtab = dst = mod->data_layout.base + info->symoffs; mod->core_kallsyms.strtab = s = mod->data_layout.base + info->stroffs; mod->core_kallsyms.typetab = mod->data_layout.base + info->core_typeoffs; + strtab_size = info->core_typeoffs - info->stroffs; src = rcu_dereference_sched(mod->kallsyms)->symtab; for (ndst = i = 0; i < rcu_dereference_sched(mod->kallsyms)->num_symtab; i++) { rcu_dereference_sched(mod->kallsyms)->typetab[i] = elf_type(src + i, info); if (i == 0 || is_livepatch_module(mod) || is_core_symbol(src + i, info->sechdrs, info->hdr->e_shnum, info->index.pcpu)) { + ssize_t ret; + mod->core_kallsyms.typetab[ndst] = rcu_dereference_sched(mod->kallsyms)->typetab[i]; dst[ndst] = src[i]; dst[ndst++].st_name = s - mod->core_kallsyms.strtab; - s += strscpy(s, - &rcu_dereference_sched(mod->kallsyms)->strtab[src[i].st_name], - KSYM_NAME_LEN) + 1; + ret = strscpy(s, + &rcu_dereference_sched(mod->kallsyms)->strtab[src[i].st_name], + strtab_size); + if (ret < 0) + break; + s += ret + 1; + strtab_size -= ret + 1; } } preempt_enable(); -- cgit v1.2.3 From cfa94c538be621a0ba645adfa9ead005b5fa02f6 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Sun, 12 Jun 2022 17:21:56 +0200 Subject: module: Fix selfAssignment cppcheck warning cppcheck reports the following warnings: kernel/module/main.c:1455:26: warning: Redundant assignment of 'mod->core_layout.size' to itself. [selfAssignment] mod->core_layout.size = strict_align(mod->core_layout.size); ^ kernel/module/main.c:1489:26: warning: Redundant assignment of 'mod->init_layout.size' to itself. [selfAssignment] mod->init_layout.size = strict_align(mod->init_layout.size); ^ kernel/module/main.c:1493:26: warning: Redundant assignment of 'mod->init_layout.size' to itself. [selfAssignment] mod->init_layout.size = strict_align(mod->init_layout.size); ^ kernel/module/main.c:1504:26: warning: Redundant assignment of 'mod->init_layout.size' to itself. [selfAssignment] mod->init_layout.size = strict_align(mod->init_layout.size); ^ kernel/module/main.c:1459:26: warning: Redundant assignment of 'mod->data_layout.size' to itself. [selfAssignment] mod->data_layout.size = strict_align(mod->data_layout.size); ^ kernel/module/main.c:1463:26: warning: Redundant assignment of 'mod->data_layout.size' to itself. [selfAssignment] mod->data_layout.size = strict_align(mod->data_layout.size); ^ kernel/module/main.c:1467:26: warning: Redundant assignment of 'mod->data_layout.size' to itself. [selfAssignment] mod->data_layout.size = strict_align(mod->data_layout.size); ^ This is due to strict_align() being a no-op when CONFIG_STRICT_MODULE_RWX is not selected. Transform strict_align() macro into an inline function. It will allow type checking and avoid the selfAssignment warning. Reported-by: kernel test robot Signed-off-by: Christophe Leroy Signed-off-by: Luis Chamberlain --- kernel/module/internal.h | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/kernel/module/internal.h b/kernel/module/internal.h index bc5507ab8450..ec104c2950c3 100644 --- a/kernel/module/internal.h +++ b/kernel/module/internal.h @@ -11,6 +11,7 @@ #include #include #include +#include #ifndef ARCH_SHF_SMALL #define ARCH_SHF_SMALL 0 @@ -30,11 +31,13 @@ * to ensure complete separation of code and data, but * only when CONFIG_STRICT_MODULE_RWX=y */ -#ifdef CONFIG_STRICT_MODULE_RWX -# define strict_align(X) PAGE_ALIGN(X) -#else -# define strict_align(X) (X) -#endif +static inline unsigned int strict_align(unsigned int size) +{ + if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) + return PAGE_ALIGN(size); + else + return size; +} extern struct mutex module_mutex; extern struct list_head modules; -- cgit v1.2.3 From f963ef123900ac534aeb6141642e5351989ac14c Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Sun, 12 Jun 2022 17:33:20 +0200 Subject: module: Fix "warning: variable 'exit' set but not used" When CONFIG_MODULE_UNLOAD is not selected, 'exit' is set but never used. It is not possible to replace the #ifdef CONFIG_MODULE_UNLOAD by IS_ENABLED(CONFIG_MODULE_UNLOAD) because mod->exit doesn't exist when CONFIG_MODULE_UNLOAD is not selected. And because of the rcu_read_lock_sched() section it is not easy to regroup everything in a single #ifdef. Let's regroup partially and add missing #ifdef to completely opt out the use of 'exit' when CONFIG_MODULE_UNLOAD is not selected. Reported-by: kernel test robot Signed-off-by: Christophe Leroy Signed-off-by: Luis Chamberlain --- kernel/module/main.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/module/main.c b/kernel/module/main.c index fed58d30725d..0548151dd933 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -2939,24 +2939,25 @@ static void cfi_init(struct module *mod) { #ifdef CONFIG_CFI_CLANG initcall_t *init; +#ifdef CONFIG_MODULE_UNLOAD exitcall_t *exit; +#endif rcu_read_lock_sched(); mod->cfi_check = (cfi_check_fn) find_kallsyms_symbol_value(mod, "__cfi_check"); init = (initcall_t *) find_kallsyms_symbol_value(mod, "__cfi_jt_init_module"); - exit = (exitcall_t *) - find_kallsyms_symbol_value(mod, "__cfi_jt_cleanup_module"); - rcu_read_unlock_sched(); - /* Fix init/exit functions to point to the CFI jump table */ if (init) mod->init = *init; #ifdef CONFIG_MODULE_UNLOAD + exit = (exitcall_t *) + find_kallsyms_symbol_value(mod, "__cfi_jt_cleanup_module"); if (exit) mod->exit = *exit; #endif + rcu_read_unlock_sched(); cfi_module_add(mod, mod_tree.addr_min); #endif -- cgit v1.2.3 From 2cc39179acbbe524127f0427cee92b629db4d64b Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Wed, 15 Jun 2022 06:33:03 +0900 Subject: doc: module: update file references Adjust documents to the file moves made by commit cfc1d277891e ("module: Move all into module/"). Thanks to Yanteng Si for helping me to update Documentation/translations/zh_CN/core-api/kernel-api.rst Signed-off-by: Masahiro Yamada Acked-by: Yanteng Si Signed-off-by: Luis Chamberlain --- Documentation/core-api/kernel-api.rst | 2 +- Documentation/core-api/symbol-namespaces.rst | 4 ++-- Documentation/livepatch/module-elf-format.rst | 10 +++++----- .../translations/it_IT/core-api/symbol-namespaces.rst | 6 +++--- Documentation/translations/zh_CN/core-api/kernel-api.rst | 2 +- .../translations/zh_CN/core-api/symbol-namespaces.rst | 2 +- 6 files changed, 13 insertions(+), 13 deletions(-) diff --git a/Documentation/core-api/kernel-api.rst b/Documentation/core-api/kernel-api.rst index d6b3f94b9f1f..0793c400d4b0 100644 --- a/Documentation/core-api/kernel-api.rst +++ b/Documentation/core-api/kernel-api.rst @@ -223,7 +223,7 @@ Module Loading Inter Module support -------------------- -Refer to the file kernel/module.c for more information. +Refer to the files in kernel/module/ for more information. Hardware Interfaces =================== diff --git a/Documentation/core-api/symbol-namespaces.rst b/Documentation/core-api/symbol-namespaces.rst index 5ad9e0abe42c..12e4aecdae94 100644 --- a/Documentation/core-api/symbol-namespaces.rst +++ b/Documentation/core-api/symbol-namespaces.rst @@ -51,8 +51,8 @@ namespace ``USB_STORAGE``, use:: The corresponding ksymtab entry struct ``kernel_symbol`` will have the member ``namespace`` set accordingly. A symbol that is exported without a namespace will refer to ``NULL``. There is no default namespace if none is defined. ``modpost`` -and kernel/module.c make use the namespace at build time or module load time, -respectively. +and kernel/module/main.c make use the namespace at build time or module load +time, respectively. 2.2 Using the DEFAULT_SYMBOL_NAMESPACE define ============================================= diff --git a/Documentation/livepatch/module-elf-format.rst b/Documentation/livepatch/module-elf-format.rst index dbe9b400e39f..7347638895a0 100644 --- a/Documentation/livepatch/module-elf-format.rst +++ b/Documentation/livepatch/module-elf-format.rst @@ -210,11 +210,11 @@ module->symtab. ===================================== Normally, a stripped down copy of a module's symbol table (containing only "core" symbols) is made available through module->symtab (See layout_symtab() -in kernel/module.c). For livepatch modules, the symbol table copied into memory -on module load must be exactly the same as the symbol table produced when the -patch module was compiled. This is because the relocations in each livepatch -relocation section refer to their respective symbols with their symbol indices, -and the original symbol indices (and thus the symtab ordering) must be +in kernel/module/kallsyms.c). For livepatch modules, the symbol table copied +into memory on module load must be exactly the same as the symbol table produced +when the patch module was compiled. This is because the relocations in each +livepatch relocation section refer to their respective symbols with their symbol +indices, and the original symbol indices (and thus the symtab ordering) must be preserved in order for apply_relocate_add() to find the right symbol. For example, take this particular rela from a livepatch module::: diff --git a/Documentation/translations/it_IT/core-api/symbol-namespaces.rst b/Documentation/translations/it_IT/core-api/symbol-namespaces.rst index 42f5d04e38ec..0f6898860d6d 100644 --- a/Documentation/translations/it_IT/core-api/symbol-namespaces.rst +++ b/Documentation/translations/it_IT/core-api/symbol-namespaces.rst @@ -50,9 +50,9 @@ Di conseguenza, nella tabella dei simboli del kernel ci sarà una voce rappresentata dalla struttura ``kernel_symbol`` che avrà il campo ``namespace`` (spazio dei nomi) impostato. Un simbolo esportato senza uno spazio dei nomi avrà questo campo impostato a ``NULL``. Non esiste uno spazio dei nomi -di base. Il programma ``modpost`` e il codice in kernel/module.c usano lo spazio -dei nomi, rispettivamente, durante la compilazione e durante il caricamento -di un modulo. +di base. Il programma ``modpost`` e il codice in kernel/module/main.c usano lo +spazio dei nomi, rispettivamente, durante la compilazione e durante il +caricamento di un modulo. 2.2 Usare il simbolo di preprocessore DEFAULT_SYMBOL_NAMESPACE ============================================================== diff --git a/Documentation/translations/zh_CN/core-api/kernel-api.rst b/Documentation/translations/zh_CN/core-api/kernel-api.rst index e45fe80d1cd8..962d31d019d7 100644 --- a/Documentation/translations/zh_CN/core-api/kernel-api.rst +++ b/Documentation/translations/zh_CN/core-api/kernel-api.rst @@ -224,7 +224,7 @@ kernel/kmod.c 模块接口支持 ------------ -更多信息请参考文件kernel/module.c。 +更多信息请参阅kernel/module/目录下的文件。 硬件接口 ======== diff --git a/Documentation/translations/zh_CN/core-api/symbol-namespaces.rst b/Documentation/translations/zh_CN/core-api/symbol-namespaces.rst index 6abf7ed534ca..bb16f0611046 100644 --- a/Documentation/translations/zh_CN/core-api/symbol-namespaces.rst +++ b/Documentation/translations/zh_CN/core-api/symbol-namespaces.rst @@ -52,7 +52,7 @@ 相应的 ksymtab 条目结构体 ``kernel_symbol`` 将有相应的成员 ``命名空间`` 集。 导出时未指明命名空间的符号将指向 ``NULL`` 。如果没有定义命名空间，则默认没有。 -``modpost`` 和kernel/module.c分别在构建时或模块加载时使用名称空间。 +``modpost`` 和kernel/module/main.c分别在构建时或模块加载时使用名称空间。 2.2 使用DEFAULT_SYMBOL_NAMESPACE定义 ==================================== -- cgit v1.2.3 From e69a66147d49506062cd837f3b230ee3e98102ab Mon Sep 17 00:00:00 2001 From: Aaron Tomlin Date: Mon, 11 Jul 2022 18:17:19 +0100 Subject: module: kallsyms: Ensure preemption in add_kallsyms() with PREEMPT_RT The commit 08126db5ff73 ("module: kallsyms: Fix suspicious rcu usage") under PREEMPT_RT=y, disabling preemption introduced an unbounded latency since the loop is not fixed. This change caused a regression since previously preemption was not disabled and we would dereference RCU-protected pointers explicitly. That being said, these pointers cannot change. Before kallsyms-specific data is prepared/or set-up, we ensure that the unformed module is known to be unique i.e. does not already exist (see load_module()). Therefore, we can fix this by using the common and more appropriate RCU flavour as this section of code can be safely preempted. Reported-by: Steven Rostedt Fixes: 08126db5ff73 ("module: kallsyms: Fix suspicious rcu usage") Signed-off-by: Aaron Tomlin Signed-off-by: Luis Chamberlain --- kernel/module/kallsyms.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c index 18c23545b984..77e75bead569 100644 --- a/kernel/module/kallsyms.c +++ b/kernel/module/kallsyms.c @@ -176,14 +176,14 @@ void add_kallsyms(struct module *mod, const struct load_info *info) mod->kallsyms = (void __rcu *)mod->init_layout.base + info->mod_kallsyms_init_off; - preempt_disable(); + rcu_read_lock(); /* The following is safe since this pointer cannot change */ - rcu_dereference_sched(mod->kallsyms)->symtab = (void *)symsec->sh_addr; - rcu_dereference_sched(mod->kallsyms)->num_symtab = symsec->sh_size / sizeof(Elf_Sym); + rcu_dereference(mod->kallsyms)->symtab = (void *)symsec->sh_addr; + rcu_dereference(mod->kallsyms)->num_symtab = symsec->sh_size / sizeof(Elf_Sym); /* Make sure we get permanent strtab: don't use info->strtab. */ - rcu_dereference_sched(mod->kallsyms)->strtab = + rcu_dereference(mod->kallsyms)->strtab = (void *)info->sechdrs[info->index.str].sh_addr; - rcu_dereference_sched(mod->kallsyms)->typetab = mod->init_layout.base + info->init_typeoffs; + rcu_dereference(mod->kallsyms)->typetab = mod->init_layout.base + info->init_typeoffs; /* * Now populate the cut down core kallsyms for after init @@ -193,20 +193,20 @@ void add_kallsyms(struct module *mod, const struct load_info *info) mod->core_kallsyms.strtab = s = mod->data_layout.base + info->stroffs; mod->core_kallsyms.typetab = mod->data_layout.base + info->core_typeoffs; strtab_size = info->core_typeoffs - info->stroffs; - src = rcu_dereference_sched(mod->kallsyms)->symtab; - for (ndst = i = 0; i < rcu_dereference_sched(mod->kallsyms)->num_symtab; i++) { - rcu_dereference_sched(mod->kallsyms)->typetab[i] = elf_type(src + i, info); + src = rcu_dereference(mod->kallsyms)->symtab; + for (ndst = i = 0; i < rcu_dereference(mod->kallsyms)->num_symtab; i++) { + rcu_dereference(mod->kallsyms)->typetab[i] = elf_type(src + i, info); if (i == 0 || is_livepatch_module(mod) || is_core_symbol(src + i, info->sechdrs, info->hdr->e_shnum, info->index.pcpu)) { ssize_t ret; mod->core_kallsyms.typetab[ndst] = - rcu_dereference_sched(mod->kallsyms)->typetab[i]; + rcu_dereference(mod->kallsyms)->typetab[i]; dst[ndst] = src[i]; dst[ndst++].st_name = s - mod->core_kallsyms.strtab; ret = strscpy(s, - &rcu_dereference_sched(mod->kallsyms)->strtab[src[i].st_name], + &rcu_dereference(mod->kallsyms)->strtab[src[i].st_name], strtab_size); if (ret < 0) break; @@ -214,7 +214,7 @@ void add_kallsyms(struct module *mod, const struct load_info *info) strtab_size -= ret + 1; } } - preempt_enable(); + rcu_read_unlock(); mod->core_kallsyms.num_symtab = ndst; } -- cgit v1.2.3