With kernel lockdown the access to kernel interfaces that allow to
extract confidential information (lockdown=confidentiality) or modify a
running kernel (lockdown=integrity) can be restricted. Two of the
interfaces that can be restricted are /dev/mem (integrity &
confidentiality) and /proc/kcore (confidentiality). With
lockdown=integrity this leads to a situation where /dev/mem exists but
is not readable while /proc/kcore exists and is readable. This breaks
crash's live debugging when it is invoked without argument, i.e.
$ crash
[...]
crash: /dev/mem: Operation not permitted
while passing /proc/kcore as image succeeds. The reason for this is that
crash always picks /dev/mem as source when it exits but doesn't check if
it is readable. Fix this by only selecting /dev/mem when it is readable.
Signed-off-by: Philipp Rudo <prudo@xxxxxxxxxx>
---
filesys.c | 2 +-
main.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/filesys.c b/filesys.c
index 3361b6c..43cbe82 100644
--- a/filesys.c
+++ b/filesys.c
@@ -3666,7 +3666,7 @@ get_live_memory_source(void)
if (pc->live_memsrc)
goto live_report;
- if (file_exists("/dev/mem", NULL))
+ if (file_readable("/dev/mem"))
pc->live_memsrc = "/dev/mem";
else if (file_exists("/proc/kcore", NULL)) {
pc->flags &= ~DEVMEM;
diff --git a/main.c b/main.c
index 71c59d2..b278c22 100644
--- a/main.c
+++ b/main.c
@@ -1119,7 +1119,7 @@ setup_environment(int argc, char **argv)
pc->flags2 |= REDZONE;
pc->confd = -2;
pc->machine_type = MACHINE_TYPE;
- if (file_exists("/dev/mem", NULL)) { /* defaults until argv[] is parsed */
+ if (file_readable("/dev/mem")) { /* defaults until argv[] is parsed */
pc->readmem = read_dev_mem;
pc->writemem = write_dev_mem;
} else if (file_exists("/proc/kcore", NULL)) {
--
2.31.1
--
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