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authorJiri Slaby <jslaby@suse.cz>2016-12-14 15:06:07 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-12-14 16:04:08 -0800
commit999898355e08ae3b92dfd0a08db706e0c6703d30 (patch)
tree3847a007de4ba475bf867802e20e836ff0d7bf4b /ipc/msg.c
parentinitramfs: allow again choice of the embedded initram compression algorithm (diff)
downloadlinux-dev-999898355e08ae3b92dfd0a08db706e0c6703d30.tar.xz
linux-dev-999898355e08ae3b92dfd0a08db706e0c6703d30.zip
ipc: msg, make msgrcv work with LONG_MIN
When LONG_MIN is passed to msgrcv, one would expect to recieve any message. But convert_mode does *msgtyp = -*msgtyp and -LONG_MIN is undefined. In particular, with my gcc -LONG_MIN produces -LONG_MIN again. So handle this case properly by assigning LONG_MAX to *msgtyp if LONG_MIN was specified as msgtyp to msgrcv. This code: long msg[] = { 100, 200 }; int m = msgget(IPC_PRIVATE, IPC_CREAT | 0644); msgsnd(m, &msg, sizeof(msg), 0); msgrcv(m, &msg, sizeof(msg), LONG_MIN, 0); produces currently nothing: msgget(IPC_PRIVATE, IPC_CREAT|0644) = 65538 msgsnd(65538, {100, "\310\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"}, 16, 0) = 0 msgrcv(65538, ... Except a UBSAN warning: UBSAN: Undefined behaviour in ipc/msg.c:745:13 negation of -9223372036854775808 cannot be represented in type 'long int': With the patch, I see what I expect: msgget(IPC_PRIVATE, IPC_CREAT|0644) = 0 msgsnd(0, {100, "\310\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"}, 16, 0) = 0 msgrcv(0, {100, "\310\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"}, 16, -9223372036854775808, 0) = 16 Link: http://lkml.kernel.org/r/20161024082633.10148-1-jslaby@suse.cz Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/msg.c')
-rw-r--r--ipc/msg.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/ipc/msg.c b/ipc/msg.c
index 32e9bd837cde..e3e52ce01123 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -763,7 +763,10 @@ static inline int convert_mode(long *msgtyp, int msgflg)
if (*msgtyp == 0)
return SEARCH_ANY;
if (*msgtyp < 0) {
- *msgtyp = -*msgtyp;
+ if (*msgtyp == LONG_MIN) /* -LONG_MIN is undefined */
+ *msgtyp = LONG_MAX;
+ else
+ *msgtyp = -*msgtyp;
return SEARCH_LESSEQUAL;
}
if (msgflg & MSG_EXCEPT)