Drop the log_size>0 and log_buf!=NULL condition when log_level>0. This
allows users to request log_true_size of a full log without providing
actual (even if small) log buffer. Verifier log handling code was mostly
ready to handle NULL log->ubuf, so only few small changes were necessary
to prevent NULL log->ubuf from causing problems.
Note, that if user provided NULL log_buf with log_level>0 we don't
consider this a log truncation, and thus won't return -ENOSPC.
We also enforce that either (log_buf==NULL && log_size==0) or
(log_buf!=NULL && log_size>0).
Suggested-by: Lorenz Bauer <lmb@xxxxxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
kernel/bpf/log.c | 42 +++++++++++++++++++++++++-----------------
1 file changed, 25 insertions(+), 17 deletions(-)
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 1fae2c5d7ae4..046ddff37a76 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -12,8 +12,17 @@
static bool bpf_verifier_log_attr_valid(const struct bpf_verifier_log *log)
{
- return log->len_total > 0 && log->len_total <= UINT_MAX >> 2 &&
- log->level && log->ubuf && !(log->level & ~BPF_LOG_MASK);
+ /* ubuf and len_total should both be specified (or not) together */
+ if (!!log->ubuf != !!log->len_total)
+ return false;
+ /* log buf without log_level is meaningless */
+ if (log->ubuf && log->level == 0)
+ return false;
+ if (log->level & ~BPF_LOG_MASK)
+ return false;
+ if (log->len_total > UINT_MAX >> 2)
+ return false;
+ return true;
}
int bpf_vlog_init(struct bpf_verifier_log *log, u32 log_level,
@@ -89,9 +98,15 @@ void bpf_verifier_vlog(struct bpf_verifier_log *log, const char *fmt,
new_start = new_end - log->len_total;
else
new_start = log->start_pos;
+
+ log->start_pos = new_start;
+ log->end_pos = new_end - 1; /* don't count terminating '\0' */
+
+ if (!log->ubuf)
+ return;
+
new_n = min(n, log->len_total);
cur_pos = new_end - new_n;
-
div_u64_rem(cur_pos, log->len_total, &buf_start);
div_u64_rem(new_end, log->len_total, &buf_end);
/* new_end and buf_end are exclusive indices, so if buf_end is
@@ -101,12 +116,6 @@ void bpf_verifier_vlog(struct bpf_verifier_log *log, const char *fmt,
if (buf_end == 0)
buf_end = log->len_total;
- log->start_pos = new_start;
- log->end_pos = new_end - 1; /* don't count terminating '\0' */
-
- if (!log->ubuf)
- return;
-
/* if buf_start > buf_end, we wrapped around;
* if buf_start == buf_end, then we fill ubuf completely; we
* can't have buf_start == buf_end to mean that there is
@@ -156,12 +165,15 @@ void bpf_vlog_reset(struct bpf_verifier_log *log, u64 new_pos)
if (log->end_pos < log->start_pos)
log->start_pos = log->end_pos;
+ if (!log->ubuf)
+ return;
+
if (log->level & BPF_LOG_FIXED)
pos = log->end_pos + 1;
else
div_u64_rem(new_pos, log->len_total, &pos);
- if (log->ubuf && pos < log->len_total && put_user(zero, log->ubuf + pos))
+ if (pos < log->len_total && put_user(zero, log->ubuf + pos))
log->ubuf = NULL;
}
@@ -211,11 +223,6 @@ static int bpf_vlog_reverse_ubuf(struct bpf_verifier_log *log, int start, int en
return 0;
}
-static bool bpf_vlog_truncated(const struct bpf_verifier_log *log)
-{
- return log->len_max > log->len_total;
-}
-
int bpf_vlog_finalize(struct bpf_verifier_log *log, u32 *log_size_actual)
{
u32 sublen;
@@ -228,7 +235,7 @@ int bpf_vlog_finalize(struct bpf_verifier_log *log, u32 *log_size_actual)
if (!log->ubuf)
goto skip_log_rotate;
/* If we never truncated log, there is nothing to move around. */
- if ((log->level & BPF_LOG_FIXED) || log->start_pos == 0)
+ if (log->start_pos == 0)
goto skip_log_rotate;
/* Otherwise we need to rotate log contents to make it start from the
@@ -283,7 +290,8 @@ int bpf_vlog_finalize(struct bpf_verifier_log *log, u32 *log_size_actual)
if (!!log->ubuf != !!log->len_total)
return -EFAULT;
- if (bpf_vlog_truncated(log))
+ /* did truncation actually happen? */
+ if (log->ubuf && log->len_max > log->len_total)
return -ENOSPC;
return 0;
--
2.34.1
