From: Sasha Levin Date: Mon, 16 Jul 2012 22:01:26 +0000 (+0200) Subject: SUNRPC: Prevent kernel stack corruption on long values of flush X-Git-Tag: v3.7-rc2~21^2 X-Git-Url: http://pileus.org/git/?p=~andy%2Flinux;a=commitdiff_plain;h=212ba90696ab4884e2025b0b13726d67aadc2cd4 SUNRPC: Prevent kernel stack corruption on long values of flush The buffer size in read_flush() is too small for the longest possible values for it. This can lead to a kernel stack corruption: [ 43.047329] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff833e64b4 [ 43.047329] [ 43.049030] Pid: 6015, comm: trinity-child18 Tainted: G W 3.5.0-rc7-next-20120716-sasha #221 [ 43.050038] Call Trace: [ 43.050435] [] panic+0xcd/0x1f4 [ 43.050931] [] ? read_flush.isra.7+0xe4/0x100 [ 43.051602] [] __stack_chk_fail+0x16/0x20 [ 43.052206] [] read_flush.isra.7+0xe4/0x100 [ 43.052951] [] ? read_flush_pipefs+0x30/0x30 [ 43.053594] [] read_flush_procfs+0x2c/0x30 [ 43.053596] [] proc_reg_read+0x9c/0xd0 [ 43.053596] [] ? proc_reg_write+0xd0/0xd0 [ 43.053596] [] do_loop_readv_writev+0x4b/0x90 [ 43.053596] [] do_readv_writev+0xf6/0x1d0 [ 43.053596] [] vfs_readv+0x3e/0x60 [ 43.053596] [] sys_readv+0x48/0xb0 [ 43.053596] [] system_call_fastpath+0x1a/0x1f Signed-off-by: Sasha Levin Cc: stable@kernel.org Signed-off-by: J. Bruce Fields --- diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c index 2a68bb3db77..fc2f7aa4dca 100644 --- a/net/sunrpc/cache.c +++ b/net/sunrpc/cache.c @@ -1409,11 +1409,11 @@ static ssize_t read_flush(struct file *file, char __user *buf, size_t count, loff_t *ppos, struct cache_detail *cd) { - char tbuf[20]; + char tbuf[22]; unsigned long p = *ppos; size_t len; - sprintf(tbuf, "%lu\n", convert_to_wallclock(cd->flush_time)); + snprintf(tbuf, sizeof(tbuf), "%lu\n", convert_to_wallclock(cd->flush_time)); len = strlen(tbuf); if (p >= len) return 0;