[PATCH v3 0/2] linux-user: two fixes to coredump generation

[PATCH v3 0/2] linux-user: two fixes to coredump generation

[Thomas Weißschuh]

Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
---
Changes in v3:
- Add braces to if statements
- Add Reviewed-by from Richard
- Link to v2: https://lore.kernel.org/r/20240107-qemu-user-dumpable-v2-0-54e3bcfc00c9@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 | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)
---
base-commit: 3f2a357b95845ea0bf7463eff6661e43b97d1afc
change-id: 20231115-qemu-user-dumpable-d499c0396103

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

[PATCH v3 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.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
---
 linux-user/elfload.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index cf9e74468b11..c5968719380a 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -4667,9 +4667,9 @@ 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 v3 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.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
---
 linux-user/elfload.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index c5968719380a..daf7ef843564 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 +4668,11 @@ 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 v3 2/2] linux-user/elfload: check PR_GET_DUMPABLE before creating coredump

[Philippe Mathieu-Daudé]

On 20/1/24 22:45, Thomas Weißschuh wrote:
> 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.
> 
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
> ---
>   linux-user/elfload.c | 6 ++++++
>   1 file changed, 6 insertions(+)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Re: [PATCH v3 1/2] linux-user/elfload: test return value of getrlimit

[Philippe Mathieu-Daudé]

On 20/1/24 22:45, Thomas Weißschuh wrote:
> Should getrlimit() fail the value of dumpsize.rlimit_cur may not be
> initialized. Avoid reading garbage data by checking the return value of
> getrlimit.
> 
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
> ---
>   linux-user/elfload.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>