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openSUSE:11.4:Update
nfs-utils
mount-catch-signals
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File mount-catch-signals of Package nfs-utils
Subject: [PATCH] mount: improve signal management when locking mtab. References: bnc#689799 As mount.nfs can run setuid it must be careful about how the user can interact with in. In particular it needs to ensure it does not respond badly to any signals that the user might be able to generate. This is particularly an issue while updating /etc/mtab (when that is not linked to /proc/mounts). If the user can generate a signal which kills mount.nfs while /etc/mtab is locked, then it will leave the file locked, and could possibly corrupt mtab (particularly if 'ulimit 1' was previously issued). Currently lock_mtab does set some handlers for signals, but not enough. It arranges for every signal up to (but not including) SIGCHLD to cause mount.nfs to unlock mdadm promptly exit ... even if the default behaviour would be to ignore the signal. SIGALRM is handled specially, and signals after SIGCHLD are left with their default behaviour. This includes for example SIGXFSZ which can be generated by the user running "ulimit 1". So: change this so that some signals are left unchanged, SIGALRM is handled as required, and all signals that the user can generate are explicitly ignored. The remainder still cause mount.nfs to print a message, unlock mtab, and exit. Signed-off-by: NeilBrown <neilb@suse.de> --- utils/mount/fstab.c | 37 ++++++++++++++++++++++++++++++++----- 1 file changed, 32 insertions(+), 5 deletions(-) --- nfs-utils-1.2.1.orig/utils/mount/fstab.c +++ nfs-utils-1.2.1/utils/mount/fstab.c @@ -331,16 +331,43 @@ lock_mtab (void) { int sig = 0; struct sigaction sa; - sa.sa_handler = handler; sa.sa_flags = 0; sigfillset (&sa.sa_mask); - while (sigismember (&sa.sa_mask, ++sig) != -1 - && sig != SIGCHLD) { - if (sig == SIGALRM) + while (sigismember (&sa.sa_mask, ++sig) != -1) { + switch(sig) { + case SIGCHLD: + case SIGKILL: + case SIGCONT: + case SIGSTOP: + /* These cannot be caught, or should not, + * so don't even try. + */ + continue; + case SIGALRM: sa.sa_handler = setlkw_timeout; - else + break; + case SIGHUP: + case SIGINT: + case SIGQUIT: + case SIGWINCH: + case SIGTSTP: + case SIGTTIN: + case SIGTTOU: + case SIGPIPE: + case SIGXFSZ: + case SIGXCPU: + /* non-priv user can cause these to be + * generated, so ignore them. + */ + sa.sa_handler = SIG_IGN; + break; + default: + /* The rest should not be possible, so just + * print a message and unlock mtab. + */ sa.sa_handler = handler; + } sigaction (sig, &sa, (struct sigaction *) 0); } signals_have_been_setup = 1;
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