Commit-Id: 77f55eac6c433e23e82a1b88b2d74f385c4c7d82 From: Prasad J Pandit Date: Tue, 26 May 2020 16:47:43 +0530 Subject: exec: set map length to zero when returning NULL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When mapping physical memory into host's virtual address space, 'address_space_map' may return NULL if BounceBuffer is in_use. Set and return '*plen = 0' to avoid later NULL pointer dereference. Reported-by: Alexander Bulekov Fixes: https://bugs.launchpad.net/qemu/+bug/1878259 Suggested-by: Paolo Bonzini Suggested-by: Peter Maydell Signed-off-by: Prasad J Pandit Message-Id: <20200526111743.428367-1-ppandit@redhat.com> Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Paolo Bonzini --- exec.c | 1 + include/exec/memory.h | 3 ++- 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/exec.c b/exec.c index bb6170dbff..467ea8cf36 100644 --- a/exec.c +++ b/exec.c @@ -3628,6 +3628,7 @@ void *address_space_map(AddressSpace *as, if (!memory_access_is_direct(mr, is_write)) { if (atomic_xchg(&bounce.in_use, true)) { rcu_read_unlock(); + *plen = 0; return NULL; } /* Avoid unbounded allocations */ diff --git a/include/exec/memory.h b/include/exec/memory.h index bd7fdd6081..af8ca7824e 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -2314,7 +2314,8 @@ bool address_space_access_valid(AddressSpace *as, hwaddr addr, hwaddr len, /* address_space_map: map a physical memory region into a host virtual address * * May map a subset of the requested range, given by and returned in @plen. - * May return %NULL if resources needed to perform the mapping are exhausted. + * May return %NULL and set *@plen to zero(0), if resources needed to perform + * the mapping are exhausted. * Use only for reads OR writes - not for read-modify-write operations. * Use cpu_register_map_client() to know when retrying the map operation is * likely to succeed.