From: Alexey Dobriyan <adobriyan@xxxxxxxxx> Subject: fs/binfmt_elf.c: coredump: allocate core ELF header on stack Comment says ELF header is "too large to be on stack". 64 bytes on 64-bit is not large by any means. Link: http://lkml.kernel.org/r/20191222143850.GA24341@avx2 Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/binfmt_elf.c | 16 +++++----------- 1 file changed, 5 insertions(+), 11 deletions(-) --- a/fs/binfmt_elf.c~elf-coredump-allocate-core-elf-header-on-stack +++ a/fs/binfmt_elf.c @@ -2186,7 +2186,7 @@ static int elf_core_dump(struct coredump int segs, i; size_t vma_data_size = 0; struct vm_area_struct *vma, *gate_vma; - struct elfhdr *elf = NULL; + struct elfhdr elf; loff_t offset = 0, dataoff; struct elf_note_info info = { }; struct elf_phdr *phdr4note = NULL; @@ -2207,10 +2207,6 @@ static int elf_core_dump(struct coredump * exists while dumping the mm->vm_next areas to the core file. */ - /* alloc memory for large data structures: too large to be on stack */ - elf = kmalloc(sizeof(*elf), GFP_KERNEL); - if (!elf) - goto out; /* * The number of segs are recored into ELF header as 16bit value. * Please check DEFAULT_MAX_MAP_COUNT definition when you modify here. @@ -2234,7 +2230,7 @@ static int elf_core_dump(struct coredump * Collect all the non-memory information about the process for the * notes. This also sets up the file header. */ - if (!fill_note_info(elf, e_phnum, &info, cprm->siginfo, cprm->regs)) + if (!fill_note_info(&elf, e_phnum, &info, cprm->siginfo, cprm->regs)) goto cleanup; has_dumped = 1; @@ -2242,7 +2238,7 @@ static int elf_core_dump(struct coredump fs = get_fs(); set_fs(KERNEL_DS); - offset += sizeof(*elf); /* Elf header */ + offset += sizeof(elf); /* Elf header */ offset += segs * sizeof(struct elf_phdr); /* Program headers */ /* Write notes phdr entry */ @@ -2285,12 +2281,12 @@ static int elf_core_dump(struct coredump shdr4extnum = kmalloc(sizeof(*shdr4extnum), GFP_KERNEL); if (!shdr4extnum) goto end_coredump; - fill_extnum_info(elf, shdr4extnum, e_shoff, segs); + fill_extnum_info(&elf, shdr4extnum, e_shoff, segs); } offset = dataoff; - if (!dump_emit(cprm, elf, sizeof(*elf))) + if (!dump_emit(cprm, &elf, sizeof(elf))) goto end_coredump; if (!dump_emit(cprm, phdr4note, sizeof(*phdr4note))) @@ -2374,8 +2370,6 @@ cleanup: kfree(shdr4extnum); kvfree(vma_filesz); kfree(phdr4note); - kfree(elf); -out: return has_dumped; } _
