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authorMiklos Szeredi <mszeredi@redhat.com>2017-11-15 11:34:58 +0100
committerAl Viro <viro@zeniv.linux.org.uk>2018-01-20 02:31:15 -0500
commitcf5eebae2cd28d37581507668605f4d23cd7218d (patch)
tree4eb7d05f8d94adf671ba5f8aa736b9f502e37d21
parentba87977a49913129962af8ac35b0e13e0fa4382d (diff)
seq_file: fix incomplete reset on read from zero offset
When resetting iterator on a zero offset we need to discard any data already in the buffer (count), and private state of the iterator (version). For example this bug results in first line being repeated in /proc/mounts if doing a zero size read before a non-zero size read. Reported-by: Rich Felker <dalias@libc.org> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Fixes: e522751d605d ("seq_file: reset iterator to first record for zero offset") Cc: <stable@vger.kernel.org> # v4.10 Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/seq_file.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/fs/seq_file.c b/fs/seq_file.c
index 4be761c1a03d..eea09f6d8830 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -181,8 +181,11 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
* if request is to read from zero offset, reset iterator to first
* record as it might have been already advanced by previous requests
*/
- if (*ppos == 0)
+ if (*ppos == 0) {
m->index = 0;
+ m->version = 0;
+ m->count = 0;
+ }
/* Don't assume *ppos is where we left it */
if (unlikely(*ppos != m->read_pos)) {

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