[PATCH v2 0/2] linux-user: two fixes to coredump generation

[PATCH v2 0/2] linux-user: two fixes to coredump generation

[Thomas Weißschuh]

Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
---
Changes in v2:
- Rebase on 8.2 master
- Resend after closed tree and holidays
- Link to v1: https://lore.kernel.org/r/20231115-qemu-user-dumpable-v1-0-edbe7f0fbb02@t-8ch.de

---
Thomas Weißschuh (2):
      linux-user/elfload: test return value of getrlimit
      linux-user/elfload: check PR_GET_DUMPABLE before creating coredump

 linux-user/elfload.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
---
base-commit: 0c1eccd368af8805ec0fb11e6cf25d0684d37328
change-id: 20231115-qemu-user-dumpable-d499c0396103

Best regards,
-- 
Thomas Weißschuh <thomas@t-8ch.de>

[PATCH v2 1/2] linux-user/elfload: test return value of getrlimit

[Thomas Weißschuh]

Should getrlimit() fail the value of dumpsize.rlimit_cur may not be
initialized. Avoid reading garbage data by checking the return value of
getrlimit.

Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
---
 linux-user/elfload.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index cf9e74468b11..74c9ecda1806 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -4667,8 +4667,7 @@ static int elf_core_dump(int signr, const CPUArchState *env)
     init_note_info(&info);
 
     errno = 0;
-    getrlimit(RLIMIT_CORE, &dumpsize);
-    if (dumpsize.rlim_cur == 0)
+    if (getrlimit(RLIMIT_CORE, &dumpsize) == 0 && dumpsize.rlim_cur == 0)
         return 0;
 
     corefile = core_dump_filename(ts);

-- 
2.43.0

[PATCH v2 2/2] linux-user/elfload: check PR_GET_DUMPABLE before creating coredump

[Thomas Weißschuh]

A process can opt-out of coredump creation by calling
prctl(PR_SET_DUMPABLE, 0).
linux-user passes this call from the guest through to the
operating system.
From there it can be read back again to avoid creating coredumps from
qemu-user itself if the guest chose so.

Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
---
 linux-user/elfload.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 74c9ecda1806..956cb3ae2da5 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -2,6 +2,7 @@
 #include "qemu/osdep.h"
 #include <sys/param.h>
 
+#include <sys/prctl.h>
 #include <sys/resource.h>
 #include <sys/shm.h>
 
@@ -4667,6 +4668,10 @@ static int elf_core_dump(int signr, const CPUArchState *env)
     init_note_info(&info);
 
     errno = 0;
+
+    if (prctl(PR_GET_DUMPABLE) == 0)
+        return 0;
+
     if (getrlimit(RLIMIT_CORE, &dumpsize) == 0 && dumpsize.rlim_cur == 0)
         return 0;
 

-- 
2.43.0

Re: [PATCH v2 0/2] linux-user: two fixes to coredump generation

[Richard Henderson]

On 1/8/24 01:01, Thomas Weißschuh wrote:
> Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
> ---
> Changes in v2:
> - Rebase on 8.2 master
> - Resend after closed tree and holidays
> - Link to v1: https://lore.kernel.org/r/20231115-qemu-user-dumpable-v1-0-edbe7f0fbb02@t-8ch.de
> 
> ---
> Thomas Weißschuh (2):
>        linux-user/elfload: test return value of getrlimit
>        linux-user/elfload: check PR_GET_DUMPABLE before creating coredump
> 
>   linux-user/elfload.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
> ---
> base-commit: 0c1eccd368af8805ec0fb11e6cf25d0684d37328
> change-id: 20231115-qemu-user-dumpable-d499c0396103
> 
> Best regards,

Both patches look good for correctness, but both have style issues: need braces on those 
if statements.

With that fixed,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

Re: Re: [PATCH v2 0/2] linux-user: two fixes to coredump generation

[Thomas Weißschuh]

On 2024-01-10 08:33:11+1100, Richard Henderson wrote:
> On 1/8/24 01:01, Thomas Weißschuh wrote:
> > Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
> > ---
> > Changes in v2:
> > - Rebase on 8.2 master
> > - Resend after closed tree and holidays
> > - Link to v1: https://lore.kernel.org/r/20231115-qemu-user-dumpable-v1-0-edbe7f0fbb02@t-8ch.de
> > 
> > ---
> > Thomas Weißschuh (2):
> >        linux-user/elfload: test return value of getrlimit
> >        linux-user/elfload: check PR_GET_DUMPABLE before creating coredump
> > 
> >   linux-user/elfload.c | 8 ++++++--
> >   1 file changed, 6 insertions(+), 2 deletions(-)
> > ---
> > base-commit: 0c1eccd368af8805ec0fb11e6cf25d0684d37328
> > change-id: 20231115-qemu-user-dumpable-d499c0396103
> > 
> > Best regards,
> 
> Both patches look good for correctness, but both have style issues: need
> braces on those if statements.
> 
> With that fixed,
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

Thanks,

I added the braces for the next revision, which I'll send after waiting
some more feedback.