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author | Rich Felker <dalias@aerifal.cx> | 2011-03-24 14:18:00 -0400 |
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committer | Rich Felker <dalias@aerifal.cx> | 2011-03-24 14:18:00 -0400 |
commit | b470030f839a375e5030ec9d44903ef7581c15a2 (patch) | |
tree | 462b1df89a3ea45bcf50b9d0a844472576ed6585 /src/signal | |
parent | 095820016689dfdc9141f477a86de22054c86078 (diff) | |
download | musl-b470030f839a375e5030ec9d44903ef7581c15a2.zip musl-b470030f839a375e5030ec9d44903ef7581c15a2.tar.gz musl-b470030f839a375e5030ec9d44903ef7581c15a2.tar.bz2 |
overhaul cancellation to fix resource leaks and dangerous behavior with signals
this commit addresses two issues:
1. a race condition, whereby a cancellation request occurring after a
syscall returned from kernelspace but before the subsequent
CANCELPT_END would cause cancellable resource-allocating syscalls
(like open) to leak resources.
2. signal handlers invoked while the thread was blocked at a
cancellation point behaved as if asynchronous cancellation mode wer in
effect, resulting in potentially dangerous state corruption if a
cancellation request occurs.
the glibc/nptl implementation of threads shares both of these issues.
with this commit, both are fixed. however, cancellation points
encountered in a signal handler will not be acted upon if the signal
was received while the thread was already at a cancellation point.
they will of course be acted upon after the signal handler returns, so
in real-world usage where signal handlers quickly return, it should
not be a problem. it's possible to solve this problem too by having
sigaction() wrap all signal handlers with a function that uses a
pthread_cleanup handler to catch cancellation, patch up the saved
context, and return into the cancellable function that will catch and
act upon the cancellation. however that would be a lot of complexity
for minimal if any benefit...
Diffstat (limited to 'src/signal')
-rw-r--r-- | src/signal/sigsuspend.c | 1 | ||||
-rw-r--r-- | src/signal/sigtimedwait.c | 1 |
2 files changed, 2 insertions, 0 deletions
diff --git a/src/signal/sigsuspend.c b/src/signal/sigsuspend.c index 6c13fce..9ee7124 100644 --- a/src/signal/sigsuspend.c +++ b/src/signal/sigsuspend.c @@ -7,6 +7,7 @@ int sigsuspend(const sigset_t *mask) int ret; CANCELPT_BEGIN; ret = syscall(__NR_rt_sigsuspend, mask, 8); + if (ret<0) CANCELPT_TRY; CANCELPT_END; return ret; } diff --git a/src/signal/sigtimedwait.c b/src/signal/sigtimedwait.c index a0edaaf..86a2c87 100644 --- a/src/signal/sigtimedwait.c +++ b/src/signal/sigtimedwait.c @@ -9,6 +9,7 @@ int sigtimedwait(const sigset_t *mask, siginfo_t *si, const struct timespec *tim CANCELPT_BEGIN; do { ret = syscall(__NR_rt_sigtimedwait, mask, si, timeout, 8); + if (ret<0) CANCELPT_TRY; } while (ret<0 && errno==EINTR); CANCELPT_END; return ret; |