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| author | Davidlohr Bueso <dave@stgolabs.net> | 2018-06-14 15:27:51 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-06-15 07:55:25 +0900 |
| commit | ec67aaa46dce26d671b46c94ac674ad0b67d044c (patch) | |
| tree | e4819ea3c6b732dfb972c6507ec9f4c962e00129 /ipc | |
| parent | f1b4bd0676c2b3d4a023cf3f5d535e618f7e6eff (diff) | |
| download | lwn-ec67aaa46dce26d671b46c94ac674ad0b67d044c.tar.gz lwn-ec67aaa46dce26d671b46c94ac674ad0b67d044c.zip | |
sysvipc/sem: mitigate semnum index against spectre v1
Both smatch and coverity are reporting potential issues with spectre
variant 1 with the 'semnum' index within the sma->sems array, ie:
ipc/sem.c:388 sem_lock() warn: potential spectre issue 'sma->sems'
ipc/sem.c:641 perform_atomic_semop_slow() warn: potential spectre issue 'sma->sems'
ipc/sem.c:721 perform_atomic_semop() warn: potential spectre issue 'sma->sems'
Avoid any possible speculation by using array_index_nospec() thus
ensuring the semnum value is bounded to [0, sma->sem_nsems). With the
exception of sem_lock() all of these are slowpaths.
Link: http://lkml.kernel.org/r/20180423171131.njs4rfm2yzyeg6do@linux-n805
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
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')
| -rw-r--r-- | ipc/sem.c | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/ipc/sem.c b/ipc/sem.c index 59a3cd1d3252..5af1943ad782 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -85,6 +85,7 @@ #include <linux/nsproxy.h> #include <linux/ipc_namespace.h> #include <linux/sched/wake_q.h> +#include <linux/nospec.h> #include <linux/uaccess.h> #include "util.h" @@ -368,6 +369,7 @@ static inline int sem_lock(struct sem_array *sma, struct sembuf *sops, int nsops) { struct sem *sem; + int idx; if (nsops != 1) { /* Complex operation - acquire a full lock */ @@ -385,7 +387,8 @@ static inline int sem_lock(struct sem_array *sma, struct sembuf *sops, * * Both facts are tracked by use_global_mode. */ - sem = &sma->sems[sops->sem_num]; + idx = array_index_nospec(sops->sem_num, sma->sem_nsems); + sem = &sma->sems[idx]; /* * Initial check for use_global_lock. Just an optimization, @@ -638,7 +641,8 @@ static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q) un = q->undo; for (sop = sops; sop < sops + nsops; sop++) { - curr = &sma->sems[sop->sem_num]; + int idx = array_index_nospec(sop->sem_num, sma->sem_nsems); + curr = &sma->sems[idx]; sem_op = sop->sem_op; result = curr->semval; @@ -718,7 +722,9 @@ static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q) * until the operations can go through. */ for (sop = sops; sop < sops + nsops; sop++) { - curr = &sma->sems[sop->sem_num]; + int idx = array_index_nospec(sop->sem_num, sma->sem_nsems); + + curr = &sma->sems[idx]; sem_op = sop->sem_op; result = curr->semval; @@ -1356,6 +1362,7 @@ static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum, return -EIDRM; } + semnum = array_index_nospec(semnum, sma->sem_nsems); curr = &sma->sems[semnum]; ipc_assert_locked_object(&sma->sem_perm); @@ -1509,6 +1516,8 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, err = -EIDRM; goto out_unlock; } + + semnum = array_index_nospec(semnum, nsems); curr = &sma->sems[semnum]; switch (cmd) { @@ -2081,7 +2090,8 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops, */ if (nsops == 1) { struct sem *curr; - curr = &sma->sems[sops->sem_num]; + int idx = array_index_nospec(sops->sem_num, sma->sem_nsems); + curr = &sma->sems[idx]; if (alter) { if (sma->complex_count) { |