There is no logic in elf_core_dump itself, or in the various arch helpers
called from it which use uaccess routines on kernel pointers except for
the file writes thate are nicely encapsulated by using __kernel_write in
dump_emit.

Signed-off-by: Christoph Hellwig <h...@lst.de>
---
 fs/binfmt_elf.c | 40 +++++++++++++---------------------------
 1 file changed, 13 insertions(+), 27 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index a1f57e20c3cf..b29b84595b09 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1355,7 +1355,6 @@ static unsigned long vma_dump_size(struct vm_area_struct 
*vma,
            vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
                u32 __user *header = (u32 __user *) vma->vm_start;
                u32 word;
-               mm_segment_t fs = get_fs();
                /*
                 * Doing it this way gets the constant folded by GCC.
                 */
@@ -1368,14 +1367,8 @@ static unsigned long vma_dump_size(struct vm_area_struct 
*vma,
                magic.elfmag[EI_MAG1] = ELFMAG1;
                magic.elfmag[EI_MAG2] = ELFMAG2;
                magic.elfmag[EI_MAG3] = ELFMAG3;
-               /*
-                * Switch to the user "segment" for get_user(),
-                * then put back what elf_core_dump() had in place.
-                */
-               set_fs(USER_DS);
                if (unlikely(get_user(word, header)))
                        word = 0;
-               set_fs(fs);
                if (word == magic.cmp)
                        return PAGE_SIZE;
        }
@@ -2183,7 +2176,6 @@ static void fill_extnum_info(struct elfhdr *elf, struct 
elf_shdr *shdr4extnum,
 static int elf_core_dump(struct coredump_params *cprm)
 {
        int has_dumped = 0;
-       mm_segment_t fs;
        int segs, i;
        size_t vma_data_size = 0;
        struct vm_area_struct *vma, *gate_vma;
@@ -2236,9 +2228,6 @@ static int elf_core_dump(struct coredump_params *cprm)
 
        has_dumped = 1;
 
-       fs = get_fs();
-       set_fs(KERNEL_DS);
-
        offset += sizeof(elf);                          /* Elf header */
        offset += segs * sizeof(struct elf_phdr);       /* Program headers */
 
@@ -2250,7 +2239,7 @@ static int elf_core_dump(struct coredump_params *cprm)
 
                phdr4note = kmalloc(sizeof(*phdr4note), GFP_KERNEL);
                if (!phdr4note)
-                       goto end_coredump;
+                       goto cleanup;
 
                fill_elf_note_phdr(phdr4note, sz, offset);
                offset += sz;
@@ -2265,7 +2254,7 @@ static int elf_core_dump(struct coredump_params *cprm)
        vma_filesz = kvmalloc(array_size(sizeof(*vma_filesz), (segs - 1)),
                              GFP_KERNEL);
        if (!vma_filesz)
-               goto end_coredump;
+               goto cleanup;
 
        for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
                        vma = next_vma(vma, gate_vma)) {
@@ -2283,17 +2272,17 @@ static int elf_core_dump(struct coredump_params *cprm)
        if (e_phnum == PN_XNUM) {
                shdr4extnum = kmalloc(sizeof(*shdr4extnum), GFP_KERNEL);
                if (!shdr4extnum)
-                       goto end_coredump;
+                       goto cleanup;
                fill_extnum_info(&elf, shdr4extnum, e_shoff, segs);
        }
 
        offset = dataoff;
 
        if (!dump_emit(cprm, &elf, sizeof(elf)))
-               goto end_coredump;
+               goto cleanup;
 
        if (!dump_emit(cprm, phdr4note, sizeof(*phdr4note)))
-               goto end_coredump;
+               goto cleanup;
 
        /* Write program headers for segments dump */
        for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
@@ -2315,22 +2304,22 @@ static int elf_core_dump(struct coredump_params *cprm)
                phdr.p_align = ELF_EXEC_PAGESIZE;
 
                if (!dump_emit(cprm, &phdr, sizeof(phdr)))
-                       goto end_coredump;
+                       goto cleanup;
        }
 
        if (!elf_core_write_extra_phdrs(cprm, offset))
-               goto end_coredump;
+               goto cleanup;
 
        /* write out the notes section */
        if (!write_note_info(&info, cprm))
-               goto end_coredump;
+               goto cleanup;
 
        if (elf_coredump_extra_notes_write(cprm))
-               goto end_coredump;
+               goto cleanup;
 
        /* Align to page */
        if (!dump_skip(cprm, dataoff - cprm->pos))
-               goto end_coredump;
+               goto cleanup;
 
        for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
                        vma = next_vma(vma, gate_vma)) {
@@ -2352,22 +2341,19 @@ static int elf_core_dump(struct coredump_params *cprm)
                        } else
                                stop = !dump_skip(cprm, PAGE_SIZE);
                        if (stop)
-                               goto end_coredump;
+                               goto cleanup;
                }
        }
        dump_truncate(cprm);
 
        if (!elf_core_write_extra_data(cprm))
-               goto end_coredump;
+               goto cleanup;
 
        if (e_phnum == PN_XNUM) {
                if (!dump_emit(cprm, shdr4extnum, sizeof(*shdr4extnum)))
-                       goto end_coredump;
+                       goto cleanup;
        }
 
-end_coredump:
-       set_fs(fs);
-
 cleanup:
        free_note_info(&info);
        kfree(shdr4extnum);
-- 
2.26.1

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