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net/bpfilter: fix dprintf usage for /dev/kmsg

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The bpfilter UMH code was recently changed to log its informative messages to
/dev/kmsg, however this interface doesn't support SEEK_CUR yet, used by
dprintf(). As result dprintf() returns -EINVAL and doesn't log anything.

However there already had some discussions about supporting SEEK_CUR into
/dev/kmsg interface in the past it wasn't concluded. Since the only user of
that from userspace perspective inside the kernel is the bpfilter UMH
(userspace) module it's better to correct it here instead waiting a conclusion
on the interface.

Fixes: 36c4357c63 ("net: bpfilter: print umh messages to /dev/kmsg")
Signed-off-by: Bruno Meneguele <bmeneg@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Bruno Meneguele 2020-03-12 20:08:20 -03:00 committed by David S. Miller
parent 0d1c3530e1
commit 13d0f7b814
1 changed files with 8 additions and 6 deletions
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14
net/bpfilter/main.c
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@ -10,7 +10,7 @@
#include <asm/unistd.h> #include <asm/unistd.h>
#include "msgfmt.h" #include "msgfmt.h"
int debug_fd; FILE *debug_f;
static int handle_get_cmd(struct mbox_request *cmd) static int handle_get_cmd(struct mbox_request *cmd)
{ {
@ -35,9 +35,10 @@ static void loop(void)
struct mbox_reply reply; struct mbox_reply reply;
int n; int n;
fprintf(debug_f, "testing the buffer\n");
n = read(0, &req, sizeof(req)); n = read(0, &req, sizeof(req));
if (n != sizeof(req)) { if (n != sizeof(req)) {
dprintf(debug_fd, "invalid request %d\n", n); fprintf(debug_f, "invalid request %d\n", n);
return; return;
} }
@ -47,7 +48,7 @@ static void loop(void)
n = write(1, &reply, sizeof(reply)); n = write(1, &reply, sizeof(reply));
if (n != sizeof(reply)) { if (n != sizeof(reply)) {
dprintf(debug_fd, "reply failed %d\n", n); fprintf(debug_f, "reply failed %d\n", n);
return; return;
} }
} }
@ -55,9 +56,10 @@ static void loop(void)
int main(void) int main(void)
{ {
debug_fd = open("/dev/kmsg", 00000002); debug_f = fopen("/dev/kmsg", "w");
dprintf(debug_fd, "Started bpfilter\n"); setvbuf(debug_f, 0, _IOLBF, 0);
fprintf(debug_f, "Started bpfilter\n");
loop(); loop();
close(debug_fd); fclose(debug_f);
return 0; return 0;
} }