From de40920f369488929456b2614b9be14242024279 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Fri, 22 Feb 2019 20:03:55 +0900 Subject: [PATCH] staging: android: ashmem: Avoid range_alloc() allocation with ashmem_mutex held. commit ecd182cbf4e107928077866399100228d2359c60 upstream. ashmem_pin() is calling range_shrink() without checking whether range_alloc() succeeded. Also, doing memory allocation with ashmem_mutex held should be avoided because ashmem_shrink_scan() tries to hold it. Therefore, move memory allocation for range_alloc() to ashmem_pin_unpin() and make range_alloc() not to fail. This patch is mostly meant for backporting purpose for fuzz testing on stable/distributor kernels, for there is a plan to remove this code in near future. Signed-off-by: Tetsuo Handa Cc: stable@vger.kernel.org Reviewed-by: Joel Fernandes Signed-off-by: Greg Kroah-Hartman --- drivers/staging/android/ashmem.c | 42 +++++++++++++++++++++++----------------- 1 file changed, 24 insertions(+), 18 deletions(-) diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c index 1cc451b..be81533 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -171,19 +171,15 @@ static inline void lru_del(struct ashmem_range *range) * @end: The ending page (inclusive) * * This function is protected by ashmem_mutex. - * - * Return: 0 if successful, or -ENOMEM if there is an error */ -static int range_alloc(struct ashmem_area *asma, - struct ashmem_range *prev_range, unsigned int purged, - size_t start, size_t end) +static void range_alloc(struct ashmem_area *asma, + struct ashmem_range *prev_range, unsigned int purged, + size_t start, size_t end, + struct ashmem_range **new_range) { - struct ashmem_range *range; - - range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL); - if (!range) - return -ENOMEM; + struct ashmem_range *range = *new_range; + *new_range = NULL; range->asma = asma; range->pgstart = start; range->pgend = end; @@ -193,8 +189,6 @@ static int range_alloc(struct ashmem_area *asma, if (range_on_lru(range)) lru_add(range); - - return 0; } /** @@ -596,7 +590,8 @@ static int get_name(struct ashmem_area *asma, void __user *name) * * Caller must hold ashmem_mutex. */ -static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend) +static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend, + struct ashmem_range **new_range) { struct ashmem_range *range, *next; int ret = ASHMEM_NOT_PURGED; @@ -649,7 +644,7 @@ static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend) * second half and adjust the first chunk's endpoint. */ range_alloc(asma, range, range->purged, - pgend + 1, range->pgend); + pgend + 1, range->pgend, new_range); range_shrink(range, range->pgstart, pgstart - 1); break; } @@ -663,7 +658,8 @@ static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend) * * Caller must hold ashmem_mutex. */ -static int ashmem_unpin(struct ashmem_area *asma, size_t pgstart, size_t pgend) +static int ashmem_unpin(struct ashmem_area *asma, size_t pgstart, size_t pgend, + struct ashmem_range **new_range) { struct ashmem_range *range, *next; unsigned int purged = ASHMEM_NOT_PURGED; @@ -689,7 +685,8 @@ restart: } } - return range_alloc(asma, range, purged, pgstart, pgend); + range_alloc(asma, range, purged, pgstart, pgend, new_range); + return 0; } /* @@ -722,10 +719,17 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, struct ashmem_pin pin; size_t pgstart, pgend; int ret = -EINVAL; + struct ashmem_range *range = NULL; if (copy_from_user(&pin, p, sizeof(pin))) return -EFAULT; + if (cmd == ASHMEM_PIN || cmd == ASHMEM_UNPIN) { + range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL); + if (!range) + return -ENOMEM; + } + mutex_lock(&ashmem_mutex); wait_event(ashmem_shrink_wait, !atomic_read(&ashmem_shrink_inflight)); @@ -750,10 +754,10 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, switch (cmd) { case ASHMEM_PIN: - ret = ashmem_pin(asma, pgstart, pgend); + ret = ashmem_pin(asma, pgstart, pgend, &range); break; case ASHMEM_UNPIN: - ret = ashmem_unpin(asma, pgstart, pgend); + ret = ashmem_unpin(asma, pgstart, pgend, &range); break; case ASHMEM_GET_PIN_STATUS: ret = ashmem_get_pin_status(asma, pgstart, pgend); @@ -762,6 +766,8 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, out_unlock: mutex_unlock(&ashmem_mutex); + if (range) + kmem_cache_free(ashmem_range_cachep, range); return ret; } -- 2.7.4