github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-07-27 09:36:22 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

netconsole: don't drop the last byte of a full-sized message

Browse Source 
nt->buf is exactly MAX_PRINT_CHUNK bytes, but scnprintf() reserves one
byte for its NUL terminator, so a non-fragmented payload of exactly
MAX_PRINT_CHUNK loses its last byte (emitted as a stray NUL in the
release path). Grow nt->buf to MAX_PRINT_CHUNK + 1 and bound the
scnprintf() calls with sizeof(nt->buf); the transmitted length stays
capped at MAX_PRINT_CHUNK.

Alternatively, nt->buf could be left at MAX_PRINT_CHUNK and the NUL byte
reserved by routing exactly-MAX_PRINT_CHUNK payloads to fragmentation
('len < MAX_PRINT_CHUNK'), at the cost of fragmenting those messages.
But it would look less sane, thus the current approach.

Fixes: c62c0a17f9 ("netconsole: Append kernel version to message")
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260616-max_print_chunk-v1-1-8dc125d67083@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Breno Leitao 2026-06-16 09:09:52 -07:00 committed by Jakub Kicinski
parent bf6e8af2c8
commit c0ebe49232
1 changed files with 7 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/net/netconsole.c
View File

@ -190,8 +190,10 @@ struct netconsole_target {
bool extended;
bool release;
struct netpoll np;
/* protected by target_list_lock */
char buf[MAX_PRINT_CHUNK];
/* protected by target_list_lock; +1 gives scnprintf() room for its
* NUL terminator so a full MAX_PRINT_CHUNK payload is not truncated
*/
char buf[MAX_PRINT_CHUNK + 1];
struct work_struct resume_wq;
};
@ -1938,7 +1940,7 @@ static void send_msg_no_fragmentation(struct netconsole_target *nt,
if (release_len) {
release = init_utsname()->release;
scnprintf(nt->buf, MAX_PRINT_CHUNK, "%s,%.*s", release,
scnprintf(nt->buf, sizeof(nt->buf), "%s,%.*s", release,
msg_len, msg);
msg_len += release_len;
} else {
@ -1947,12 +1949,12 @@ static void send_msg_no_fragmentation(struct netconsole_target *nt,
if (userdata)
msg_len += scnprintf(&nt->buf[msg_len],
MAX_PRINT_CHUNK - msg_len, "%s",
sizeof(nt->buf) - msg_len, "%s",
userdata);
if (sysdata)
msg_len += scnprintf(&nt->buf[msg_len],
MAX_PRINT_CHUNK - msg_len, "%s",
sizeof(nt->buf) - msg_len, "%s",
sysdata);
send_udp(nt, nt->buf, msg_len);