core_pattern: ignore RLIMIT_CORE if core_pattern is a pipe

For some time /proc/sys/kernel/core_pattern has been able to set its output
destination as a pipe, allowing a user space helper to receive and
intellegently process a core.  This infrastructure however has some
shortcommings which can be enhanced.  Specifically:

1) The coredump code in the kernel should ignore RLIMIT_CORE limitation
   when core_pattern is a pipe, since file system resources are not being
   consumed in this case, unless the user application wishes to save the core,
   at which point the app is restricted by usual file system limits and
   restrictions.

2) The core_pattern code should be able to parse and pass options to the
   user space helper as an argv array.  The real core limit of the uid of the
   crashing proces should also be passable to the user space helper (since it
   is overridden to zero when called).

3) Some miscellaneous bugs need to be cleaned up (specifically the
   recognition of a recursive core dump, should the user mode helper itself
   crash.  Also, the core dump code in the kernel should not wait for the user
   mode helper to exit, since the same context is responsible for writing to
   the pipe, and a read of the pipe by the user mode helper will result in a
   deadlock.

This patch:

Remove the check of RLIMIT_CORE if core_pattern is a pipe.  In the event that
core_pattern is a pipe, the entire core will be fed to the user mode helper.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Cc: <martin.pitt@ubuntu.com>
Cc: <wwoods@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 3 deletions

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 2f31c4c3fd48..3dc6a123fa10 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -52,7 +52,7 @@ static unsigned long elf_map (struct file *, unsigned long, struct elf_phdr *, i
  * don't even try.
  */
 #if defined(USE_ELF_CORE_DUMP) && defined(CONFIG_ELF_CORE)
-static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file);
+static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file, unsigned long limit);
 #else
 #define elf_core_dump   NULL
 #endif
@@ -1488,7 +1488,7 @@ static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
  * and then they are actually written out.  If we run out of core limit
  * we just truncate.
  */
-static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file)
+static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file, unsigned long limit)
 {
 #define NUM_NOTES       6
         int has_dumped = 0;
@@ -1499,7 +1499,6 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file)
         struct vm_area_struct *vma, *gate_vma;
         struct elfhdr *elf = NULL;
         loff_t offset = 0, dataoff, foffset;
-        unsigned long limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
         int numnote;
         struct memelfnote *notes = NULL;
         struct elf_prstatus *prstatus = NULL;   /* NT_PRSTATUS */