evie/android_kernel_oneplus_msm8998
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kernfs: Fix range checks in kernfs_get_target_path

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[ Upstream commit a75e78f21f9ad4b810868c89dbbabcc3931591ca ]

The terminating NUL byte is only there because the buffer is
allocated with kzalloc(PAGE_SIZE, GFP_KERNEL), but since the
range-check is off-by-one, and PAGE_SIZE==PATH_MAX, the
returned string may not be zero-terminated if it is exactly
PATH_MAX characters long.  Furthermore also the initial loop
may theoretically exceed PATH_MAX and cause a fault.

Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Bernd Edlinger 2018-07-07 17:52:47 +00:00 • committed by Greg Kroah-Hartman
parent 709426fc57
commit 39bd6a7496
1 changed files with 4 additions and 1 deletions
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5
fs/kernfs/symlink.c
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@ -63,6 +63,9 @@ static int kernfs_get_target_path(struct kernfs_node *parent,
if (base == kn) if (base == kn)
break; break;
if ((s - path) + 3 >= PATH_MAX)
return -ENAMETOOLONG;
strcpy(s, "../"); strcpy(s, "../");
s += 3; s += 3;
base = base->parent; base = base->parent;
@ -79,7 +82,7 @@ static int kernfs_get_target_path(struct kernfs_node *parent,
if (len < 2) if (len < 2)
return -EINVAL; return -EINVAL;
len--; len--;
if ((s - path) + len > PATH_MAX) if ((s - path) + len >= PATH_MAX)
return -ENAMETOOLONG; return -ENAMETOOLONG;
/* reverse fillup of target string from target to base */ /* reverse fillup of target string from target to base */