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| author | Peter Maydell <peter.maydell@linaro.org> | 2016-07-18 15:36:00 +0100 |
|---|---|---|
| committer | Riku Voipio <riku.voipio@linaro.org> | 2016-10-21 15:19:41 +0300 |
| commit | 04c95f4da7f657a0bef17d115d0a5ca2ac0e2d22 (patch) | |
| tree | 736a7cadc4ba8bec87fa81acc274ceeb152df7c4 /linux-user | |
| parent | 434f286bbc1570b204ac2a450d92890578594773 (diff) | |
| download | qemu-04c95f4da7f657a0bef17d115d0a5ca2ac0e2d22.tar.gz | |
linux-user: Don't use alloca() for epoll_wait's epoll event array
The epoll event array which epoll_wait() allocates has a size
determined by the guest which could potentially be quite large.
Use g_try_new() rather than alloca() so that we can fail more
cleanly if the guest hands us an oversize value. (ENOMEM is
not a documented return value for epoll_wait() but in practice
some kernel configurations can return it -- see for instance
sys_oabi_epoll_wait() on ARM.)
This rearrangement includes fixing a bug where we were
incorrectly passing a negative length to unlock_user() in
the error-exit codepath.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
Diffstat (limited to 'linux-user')
| -rw-r--r-- | linux-user/syscall.c | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 31143b38fe..932d0ecec3 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -11777,7 +11777,12 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, goto efault; } - ep = alloca(maxevents * sizeof(struct epoll_event)); + ep = g_try_new(struct epoll_event, maxevents); + if (!ep) { + unlock_user(target_ep, arg2, 0); + ret = -TARGET_ENOMEM; + break; + } switch (num) { #if defined(TARGET_NR_epoll_pwait) @@ -11795,8 +11800,8 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, target_set = lock_user(VERIFY_READ, arg5, sizeof(target_sigset_t), 1); if (!target_set) { - unlock_user(target_ep, arg2, 0); - goto efault; + ret = -TARGET_EFAULT; + break; } target_to_host_sigset(set, target_set); unlock_user(target_set, arg5, 0); @@ -11824,8 +11829,12 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, target_ep[i].events = tswap32(ep[i].events); target_ep[i].data.u64 = tswap64(ep[i].data.u64); } + unlock_user(target_ep, arg2, + ret * sizeof(struct target_epoll_event)); + } else { + unlock_user(target_ep, arg2, 0); } - unlock_user(target_ep, arg2, ret * sizeof(struct target_epoll_event)); + g_free(ep); break; } #endif |