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@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index e79e5a7..6bf11c1 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -2186,7 +2186,7 @@ static int elf_core_dump(struct coredump_params *cprm)
        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_params *cprm)
         * 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_params *cprm)
         * 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_params *cprm)
        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_params *cprm)
                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;
 }