From 932a134abeac597f18c86c513704709ad154994b Mon Sep 17 00:00:00 2001 From: Arun KS Date: Mon, 19 Aug 2013 12:06:33 +0530 Subject: seq_file: Fix overflow condition in seq_commit seq_path()/seq_commit() is treating a d_path() failure as an overflow condition, but it isn't. seq_read handles overflow by reallocating more buffer. And this continues in a loop utill we increase the size of seq buf beyond KMALLOC_MAX_SIZE and hence a WARN_ON. [ 363.192565] ------------[ cut here ]------------ [ 363.199462] WARNING: at mm/slab_common.c:377 kmalloc_slab+0x34/0x9c() [ 363.208557] Modules linked in: [ 363.212219] CPU: 1 PID: 1742 Comm: Binder_2 Tainted: G W3.10.0+ #17 [ 363.222930] [] (unwind_backtrace+0x0/0x11c) from[] (show_stack+0x10/0x14) [ 363.235229] [] (show_stack+0x10/0x14) from [](warn_slowpath_common+0x4c/0x68) [ 363.247253] [] (warn_slowpath_common+0x4c/0x68) from[] (warn_slowpath_null+0x18/0x1c) [ 363.259307] [] (warn_slowpath_null+0x18/0x1c) from[] (kmalloc_slab+0x34/0x9c) [ 363.270812] [] (kmalloc_slab+0x34/0x9c) from [](__kmalloc+0x14/0x1fc) [ 363.281433] [] (__kmalloc+0x14/0x1fc) from [](seq_read+0x24c/0x438) [ 363.291992] [] (seq_read+0x24c/0x438) from [](vfs_read+0xac/0x124) [ 363.302398] [] (vfs_read+0xac/0x124) from [](SyS_read+0x3c/0x60) [ 363.312591] [] (SyS_read+0x3c/0x60) from [](ret_fast_syscall+0x0/0x48) [ 363.323303] ---[ end trace 46c6467e2db7bcd4 ]--- Pass -ENOBUFS to seq_commit to signal an overflow condition and a negative value for all other errors. Signed-off-by: Arun KS --- fs/seq_file.c | 6 +++--- include/linux/seq_file.h | 12 +++++++----- 2 files changed, 10 insertions(+), 8 deletions(-) diff --git a/fs/seq_file.c b/fs/seq_file.c index 3135c25..6a33f9c 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -463,7 +463,7 @@ int seq_path(struct seq_file *m, const struct path *path, const char *esc) { char *buf; size_t size = seq_get_buf(m, &buf); - int res = -1; + int res = -ENOBUFS; if (size) { char *p = d_path(path, buf, size); @@ -487,7 +487,7 @@ int seq_path_root(struct seq_file *m, const struct path *path, { char *buf; size_t size = seq_get_buf(m, &buf); - int res = -ENAMETOOLONG; + int res = -ENOBUFS; if (size) { char *p; @@ -516,7 +516,7 @@ int seq_dentry(struct seq_file *m, struct dentry *dentry, const char *esc) { char *buf; size_t size = seq_get_buf(m, &buf); - int res = -1; + int res = -ENOBUFS; if (size) { char *p = dentry_path(dentry, buf, size); diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h index 4e32edc..43f51a0 100644 --- a/include/linux/seq_file.h +++ b/include/linux/seq_file.h @@ -7,6 +7,7 @@ #include #include #include +#include struct seq_operations; struct file; @@ -66,16 +67,17 @@ static inline size_t seq_get_buf(struct seq_file *m, char **bufp) * @num: the number of bytes to commit * * Commit @num bytes of data written to a buffer previously acquired - * by seq_buf_get. To signal an error condition, or that the data - * didn't fit in the available space, pass a negative @num value. + * by seq_buf_get. To signal an overflow condition(data didn't fit + * in the available space), pass -ENOBUFS and for other errors pass a + * negative @num value. */ static inline void seq_commit(struct seq_file *m, int num) { - if (num < 0) { - m->count = m->size; - } else { + if (num >= 0) { BUG_ON(m->count + num > m->size); m->count += num; + } else if (num == -ENOBUFS) + m->count = m->size; } } -- 1.8.2