Messages in this thread Patch in this message | | | Date | Fri, 10 Aug 2012 15:07:09 -0400 | From | Jeff Mahoney <> | Subject | [PATCH] printk: Fix calculation of length used to discard records |
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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@kernel.org Signed-off-by: Jeff Mahoney <jeffm@suse.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
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