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Date: Fri, 10 Aug 2012 15:07:09 -0400 From: Jeff Mahoney <jeffm@...e.com> To: Linus Torvalds <torvalds@...ux-foundation.org>, Kay Sievers <kay@...y.org> Cc: stable@...nel.org, Linux Kernel Maling List <linux-kernel@...r.kernel.org> Subject: [PATCH] printk: Fix calculation of length used to discard records While tracking down a weird buffer overflow issue in a program that looked to be sane, I started double checking the length returned by syslog(SYSLOG_ACTION_READ_ALL, ...) to make sure it wasn't overflowing the buffer. Sure enough, it was. I saw this in strace: 11339 syslog(SYSLOG_ACTION_READ_ALL, "<5>[244017.708129] REISERFS (dev"..., 8192) = 8279 It turns out that the loops that calculate how much space the entries will take when they're copied don't include the newlines and prefixes that will be included in the final output since prev flags is passed as 0. This patch properly accounts for it and fixes the overflow. CC: stable@...nel.org Signed-off-by: Jeff Mahoney <jeffm@...e.com> --- kernel/printk.c | 2 ++ 1 file changed, 2 insertions(+) --- a/kernel/printk.c +++ b/kernel/printk.c @@ -1034,6 +1034,7 @@ static int syslog_print_all(char __user struct log *msg = log_from_idx(idx); len += msg_print_text(msg, prev, true, NULL, 0); + prev = msg->flags; idx = log_next(idx); seq++; } @@ -1046,6 +1047,7 @@ static int syslog_print_all(char __user struct log *msg = log_from_idx(idx); len -= msg_print_text(msg, prev, true, NULL, 0); + prev = msg->flags; idx = log_next(idx); seq++; } -- Jeff Mahoney SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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