coredump: fix dumping through pipes

The offset in the core file used to be tracked with ->written field of
the coredump_params structure. The field was retired in favour of
file->f_pos.

However, ->f_pos is not maintained for pipes which leads to breakage.

Restore explicit tracking of the offset in coredump_params. Introduce
->pos field for this purpose since ->written was already reused.

Fixes: a00839395103 ("get rid of coredump_params->written").

Reported-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Signed-off-by: Mateusz Guzik <mguzik@redhat.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

5 files changed, 7 insertions, 4 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/coredump.c b/arch/powerpc/platforms/cell/spufs/coredump.c
index 84fb984f29c1..85c85eb3e245 100644
--- a/arch/powerpc/platforms/cell/spufs/coredump.c
+++ b/arch/powerpc/platforms/cell/spufs/coredump.c
@@ -172,7 +172,7 @@ static int spufs_arch_write_note(struct spu_context *ctx, int i,
         if (rc < 0)
                 goto out;
 
-        skip = roundup(cprm->file->f_pos - total + sz, 4) - cprm->file->f_pos;
+        skip = roundup(cprm->pos - total + sz, 4) - cprm->pos;
         if (!dump_skip(cprm, skip))
                 goto Eio;
 out:
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index e158b22ef32f..a7a28110dc80 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -2275,7 +2275,7 @@ static int elf_core_dump(struct coredump_params *cprm)
                 goto end_coredump;
 
         /* Align to page */
-        if (!dump_skip(cprm, dataoff - cprm->file->f_pos))
+        if (!dump_skip(cprm, dataoff - cprm->pos))
                 goto end_coredump;
 
         for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 71ade0e556b7..203589311bf8 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -1787,7 +1787,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
                                 goto end_coredump;
         }
 
-        if (!dump_skip(cprm, dataoff - cprm->file->f_pos))
+        if (!dump_skip(cprm, dataoff - cprm->pos))
                 goto end_coredump;
 
         if (!elf_fdpic_dump_segments(cprm))
diff --git a/fs/coredump.c b/fs/coredump.c
index 38a7ab87e10a..281b768000e6 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -794,6 +794,7 @@ int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
                         return 0;
                 file->f_pos = pos;
                 cprm->written += n;
+                cprm->pos += n;
                 nr -= n;
         }
         return 1;
@@ -808,6 +809,7 @@ int dump_skip(struct coredump_params *cprm, size_t nr)
                 if (dump_interrupted() ||
                     file->f_op->llseek(file, nr, SEEK_CUR) < 0)
                         return 0;
+                cprm->pos += nr;
                 return 1;
         } else {
                 while (nr > PAGE_SIZE) {
@@ -822,7 +824,7 @@ EXPORT_SYMBOL(dump_skip);
 
 int dump_align(struct coredump_params *cprm, int align)
 {
-        unsigned mod = cprm->file->f_pos & (align - 1);
+        unsigned mod = cprm->pos & (align - 1);
         if (align & (align - 1))
                 return 0;
         return mod ? dump_skip(cprm, align - mod) : 1;
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 576e4639ca60..314b3caa701c 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -65,6 +65,7 @@ struct coredump_params {
         unsigned long limit;
         unsigned long mm_flags;
         loff_t written;
+        loff_t pos;
 };
 
 /*