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>

3 files changed, 10 insertions, 15 deletions

diff --git a/arch/mips/kernel/irixelf.c b/arch/mips/kernel/irixelf.c
index 5a3fe43e301..b997af713eb 100644
--- a/arch/mips/kernel/irixelf.c
+++ b/arch/mips/kernel/irixelf.c
@@ -44,7 +44,7 @@
 static int load_irix_binary(struct linux_binprm * bprm, struct pt_regs * regs);
 static int load_irix_library(struct file *);
 static int irix_core_dump(long signr, struct pt_regs * regs,
-                          struct file *file);
+                          struct file *file, unsigned long limit);
 
 static struct linux_binfmt irix_format = {
         .module         = THIS_MODULE,
@@ -1091,7 +1091,7 @@ end_coredump:
  * and then they are actually written out.  If we run out of core limit
  * we just truncate.
  */
-static int irix_core_dump(long signr, struct pt_regs * regs, struct file *file)
+static int irix_core_dump(long signr, struct pt_regs *regs, struct file *file, unsigned long limit)
 {
         int has_dumped = 0;
         mm_segment_t fs;
@@ -1101,7 +1101,6 @@ static int irix_core_dump(long signr, struct pt_regs * regs, struct file *file)
         struct vm_area_struct *vma;
         struct elfhdr elf;
         off_t offset = 0, dataoff;
-        int limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
         int numnote = 3;
         struct memelfnote notes[3];
         struct elf_prstatus prstatus;   /* NT_PRSTATUS */
diff --git a/arch/sparc64/kernel/binfmt_aout32.c b/arch/sparc64/kernel/binfmt_aout32.c
index c8acbeab49b..92c1b36a2e1 100644
--- a/arch/sparc64/kernel/binfmt_aout32.c
+++ b/arch/sparc64/kernel/binfmt_aout32.c
@@ -35,7 +35,7 @@
 
 static int load_aout32_binary(struct linux_binprm *, struct pt_regs * regs);
 static int load_aout32_library(struct file*);
-static int aout32_core_dump(long signr, struct pt_regs * regs, struct file *file);
+static int aout32_core_dump(long signr, struct pt_regs *regs, struct file *file, unsigned long limit);
 
 static struct linux_binfmt aout32_format = {
         .module         = THIS_MODULE,
@@ -86,7 +86,7 @@ if (file->f_op->llseek) { \
  * dumping of the process results in another error..
  */
 
-static int aout32_core_dump(long signr, struct pt_regs *regs, struct file *file)
+static int aout32_core_dump(long signr, struct pt_regs *regs, struct file *file, unsigned long limit)
 {
         mm_segment_t fs;
         int has_dumped = 0;
@@ -105,13 +105,11 @@ static int aout32_core_dump(long signr, struct pt_regs *regs, struct file *file)
 
 /* If the size of the dump file exceeds the rlimit, then see what would happen
    if we wrote the stack, but not the data area.  */
-        if ((dump.u_dsize+dump.u_ssize) >
-            current->signal->rlim[RLIMIT_CORE].rlim_cur)
+        if (dump.u_dsize + dump.u_ssize > limit)
                 dump.u_dsize = 0;
 
 /* Make sure we have enough room to write the stack and data areas. */
-        if ((dump.u_ssize) >
-            current->signal->rlim[RLIMIT_CORE].rlim_cur)
+        if (dump.u_ssize > limit)
                 dump.u_ssize = 0;
 
 /* make sure we actually have a data and stack area to dump */
diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
index 08781370256..7cf1c29bf90 100644
--- a/arch/x86/ia32/ia32_aout.c
+++ b/arch/x86/ia32/ia32_aout.c
@@ -40,7 +40,7 @@ static int load_aout_binary(struct linux_binprm *, struct pt_regs * regs);
 static int load_aout_library(struct file*);
 
 #ifdef CORE_DUMP
-static int aout_core_dump(long signr, struct pt_regs * regs, struct file *file);
+static int aout_core_dump(long signr, struct pt_regs *regs, struct file *file, unsigned long limit);
 
 /*
  * fill in the user structure for a core dump..
@@ -148,7 +148,7 @@ if (file->f_op->llseek) { \
  * dumping of the process results in another error..
  */
 
-static int aout_core_dump(long signr, struct pt_regs * regs, struct file *file)
+static int aout_core_dump(long signr, struct pt_regs *regs, struct file *file, unsigned long limit)
 {
         mm_segment_t fs;
         int has_dumped = 0;
@@ -168,13 +168,11 @@ static int aout_core_dump(long signr, struct pt_regs * regs, struct file *file)
 
 /* If the size of the dump file exceeds the rlimit, then see what would happen
    if we wrote the stack, but not the data area.  */
-        if ((dump.u_dsize+dump.u_ssize+1) * PAGE_SIZE >
-            current->signal->rlim[RLIMIT_CORE].rlim_cur)
+        if ((dump.u_dsize + dump.u_ssize + 1) * PAGE_SIZE > limit)
                 dump.u_dsize = 0;
 
 /* Make sure we have enough room to write the stack and data areas. */
-        if ((dump.u_ssize+1) * PAGE_SIZE >
-            current->signal->rlim[RLIMIT_CORE].rlim_cur)
+        if ((dump.u_ssize + 1) * PAGE_SIZE > limit)
                 dump.u_ssize = 0;
 
 /* make sure we actually have a data and stack area to dump */