From f9d69d5e7bde2295eb7488a56f094ac8f5383b92 Mon Sep 17 00:00:00 2001 From: Ihor Solodrai Date: Tue, 30 Dec 2025 10:32:08 -0800 Subject: module: Fix kernel panic when a symbol st_shndx is out of bounds The module loader doesn't check for bounds of the ELF section index in simplify_symbols(): for (i = 1; i < symsec->sh_size / sizeof(Elf_Sym); i++) { const char *name = info->strtab + sym[i].st_name; switch (sym[i].st_shndx) { case SHN_COMMON: [...] default: /* Divert to percpu allocation if a percpu var. */ if (sym[i].st_shndx == info->index.pcpu) secbase = (unsigned long)mod_percpu(mod); else /** HERE --> **/ secbase = info->sechdrs[sym[i].st_shndx].sh_addr; sym[i].st_value += secbase; break; } } A symbol with an out-of-bounds st_shndx value, for example 0xffff (known as SHN_XINDEX or SHN_HIRESERVE), may cause a kernel panic: BUG: unable to handle page fault for address: ... RIP: 0010:simplify_symbols+0x2b2/0x480 ... Kernel panic - not syncing: Fatal exception This can happen when module ELF is legitimately using SHN_XINDEX or when it is corrupted. Add a bounds check in simplify_symbols() to validate that st_shndx is within the valid range before using it. This issue was discovered due to a bug in llvm-objcopy, see relevant discussion for details [1]. [1] https://lore.kernel.org/linux-modules/20251224005752.201911-1-ihor.solodrai@linux.dev/ Signed-off-by: Ihor Solodrai Reviewed-by: Daniel Gomez Reviewed-by: Petr Pavlu Signed-off-by: Sami Tolvanen --- kernel/module/main.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'kernel/module') diff --git a/kernel/module/main.c b/kernel/module/main.c index eec6c9cf8dbb..c3ce106c70af 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -1568,6 +1568,13 @@ static int simplify_symbols(struct module *mod, const struct load_info *info) break; default: + if (sym[i].st_shndx >= info->hdr->e_shnum) { + pr_err("%s: Symbol %s has an invalid section index %u (max %u)\n", + mod->name, name, sym[i].st_shndx, info->hdr->e_shnum - 1); + ret = -ENOEXEC; + break; + } + /* Divert to percpu allocation if a percpu var. */ if (sym[i].st_shndx == info->index.pcpu) secbase = (unsigned long)mod_percpu(mod); -- cgit v1.2.3